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shader-xna.doc
E.R.M.A. Razab-Sekh (1204424)
Table of Contents
Introduction ................................................................................................................................ 2
Required development tools .................................................................................................. 2
Required knowledge .............................................................................................................. 2
About shaders............................................................................................................................. 3
HLSL...................................................................................................................................... 4
Shader effects ............................................................................................................................. 5
Vertex Shaders ....................................................................................................................... 5
Geometry shaders................................................................................................................... 5
Pixel Shaders .......................................................................................................................... 5
Effects ........................................................................................................................................ 7
Examining a Simple Effect .................................................................................................... 7
HLSL Semantics .................................................................................................................... 8
HLSL Types ........................................................................................................................... 8
Effect Parameters ................................................................................................................... 9
Uniform and Varying Inputs ................................................................................................ 10
Shader functions....................................................................................................................... 11
Vertex Shader Function ....................................................................................................... 11
Pixel Shader Function .......................................................................................................... 12
State Setting ......................................................................................................................... 13
Example: Vertex lighting ......................................................................................................... 14
Using an effect in an XNA game ......................................................................................... 15
Flatshaded Effect ................................................................................................................. 16
VertexLighting Effect .......................................................................................................... 17
Lambertian lighting explained ...................................................................................................... 18
1
Introduction
Required development tools
In this document there is a code example of a vertex lighting shader effect, which is written in
C#, and needs to be compiled and runned with the XNA Game Studio Express IDE.
To use XNA Game Studio Express, Microsoft .NET 2.0 and Microsoft Visual Studio 2005
(C#) must be installed.
Required knowledge
Some knowledge of programming data structures is required.
The reader should also have some mathematical knowledge about vectors and matrices.
Purpose of this document
The goal of this document is introduce the reader to the concept of shaders, and to give the
reader a basic understanding of various shader effects that are frequently used. There will
also be an example of how to implement a basic shader effect with XNA (vertex lighting).
2
About shaders
Microsoft introduced a new feature in version 7 of its DirectX API: hardware T&L
(hardware transformation and lighting). The new technology moved the expensive vertex
transformation and lighting calculations from the CPU to the GPU. This was a very
interesting feature that would lead to an increasing demand for more powerful GPUs to run
3D programs. Because shader effects became more intricate and expensive (resulting in a
demand for more powerful GPUs), CPU power to run sophisticated graphics programs
became less necessary.
The DirectX 7 API exposed an elaborate set of state values that allowed a fixed number of
lights, textures, and other states to be applied to a given draw function.
While hardware texturing and lighting had an incredible impact on the quality of 3D graphics
on the personal computer, there was a significant drawback. The calculations used to light
and display the world were hard-wired on the GPU. As a result, games of that time began to
look very similar, since they couldn’t differentiate their lighting models except by applying
different states.
In the field of offline software image rendering for movie special effects, small programs or
functions called shaders were increasingly being used to define custom interactions between a
variety of materials and lighting conditions.
In 2002, the first consumer level programmable GPUs became available and game developers
began to make use of the new functionality. Most early consumers of programmable GPUs
associated shaders with the classic rippling water effect, which at the time was considered the
height of real-time graphical “eye candy.”
A common misconception is that shaders can only be used for 3D graphics. However,
shader functions can be used in 2D applications too to render graphics (for example to render
rectangles or post-processing effect like blooming/blurring).
DirectX 8.0 was the first Microsoft graphics API to support programmable shaders, though
initially, all shader programs had to be written in assembly code. As shader hardware
increased in complexity, so did the programs. High-level shading languages were introduced
to make shader development manageable. Today, Microsoft high-level shader language
(HLSL) is the standard language used by all Microsoft 3D APIs, including the XNA
Framework. The language compiles directly to the byte code used to execute shaders on
GPUs.
Shaders have evolved greatly over the years. Generations of shader hardware are usually
categorized by the DirectX shader models they support. Early shader models had extreme
limits on the kinds and number of instructions that could be run on each vertex or pixel. Later
models defined more instructions, added larger numbers of instructions per shader program,
and enabled looping and branching functionality. Shader models correspond to a "generation"
of hardware feature sets that define such things as the supported number of operations per
pass, intrinsic functions, and supported control statements.
Many XNA Windows materials are written with a minimum bar of Shader Model 2.0, while
3
the Xbox 360 platform supports its own version of Shader Model 3.0.
For the included XNA code sample, Shader Model 2.0 was chosen since it would target
widely available computer hardware.
HLSL
HLSL (High Level Shading Language) is a shading language developed by Microsoft for use
with the Microsoft Direct3D API. It is analogous to the GLSL shading language used with
the OpenGL standard. It is very similar to the NVIDIA Cg shading language, as it was
developed alongside it.
HLSL programs come in three forms: vertex shaders, geometry shaders, and pixel shaders.
A vertex shader is executed for each vertex that is submitted by the application, and is
primarily responsible for transforming the vertex from object space to view space, generating
texture coordinates, and calculating lighting coefficients such as the vertex's tangent,
binormal and normal vectors. When a group of vertices (normally 3, to form a triangle) come
through the vertex shader, their output position is interpolated to form pixels within its area.
This process is known as rasterisation. Each of these pixels comes through the pixel shader,
whereby the resultant screen colour is calculated.
Optionally, an application using a Direct3D10 interface and Direct3D10 hardware may also
specify a geometry shader. This shader takes as its input the three vertices of a triangle and
uses this data to generate additional triangles, which are each then sent to the rasterizer.
4
Shader effects
Vertex Shaders
Vertex shaders expose functionality that was originally hard-coded into fixed-function
hardware texture and lighting. Vertex shader programs are functions run once on each vertex
passed into a Draw call. They are responsible for transforming raw, unlit vertices into
processed vertex data usable by the rest of the graphics pipeline. The input of the vertex
shader corresponds to the untransformed data in the vertex buffer.
At the bare minimum, a vertex shader only needs to return a transformed position.
Geometry shaders
A geometry shader can generate new primitives from existing primitives like pixels, lines and
triangles.
Geometry shader is executed after Vertex shader and its input is the whole primitive or
primitive with adjacency information. For example, when operating on triangles, three
vertices are geometry shader's input. Geometry shader can then emit zero or more primitives,
which are rasterized and their fragments ultimately passed to Pixel shader.
Typical uses of a geometry shader include point sprite generation, geometry tessellation,
shadow volume extrusion, single pass rendering to a cube map.
A geometry shader begins with a single primitive (point, line, triangle). It can read the
attributes of any of the vertices in the primitive and use them to generate new primitives. A
geometry shader has a fixed output primitive type (point, line strip, or triangle strip) and
emits vertices to define a new primitive. A geometry shader can emit multiple disconnected
primitives.
Pixel Shaders
Pixel shaders add a level of control not available in classic fixed-function pipelines. To
understand a pixel shader, we need to know more about what happens after the vertex shader
runs. The processed vertex data is used to set up triangles, which in turn are used to
determine which pixels on the screen will be drawn. The input to the pixel shader is
calculated using the vertex shader outputs from each of the triangle's three vertices.
The inputs of a pixel shader function are therefore bound to the outputs of the vertex shader.
So if a vertex shader returns color data, the pixel shader inputs may include this color data.
The data is typically interpolated using the three surrounding vertices. For example, imagine
an equilateral triangle. Each of its three vertices is a different color. One is red, one is green,
and one is blue. The color input to the pixel shader will be calculated by linear interpolation
on those three colors. Pixels that are close to the red vertex will be mostly red, pixels that are
closer to the blue vertex will be blue, and the pixel in the exact center of the triangle will have
equal parts of red, green, and blue.
5
At a minimum, pixel shaders must output color data. Pixel shader outputs translate directly
into the colors seen on the screen. Pixel shaders are primarily used for a number of per-pixel
color operations, including texturing, lighting, and image processing.
6
Effects
Effects combine the ideas of vertex shaders, pixel shaders, and graphics device states into one
common file format. XNA supports shaders primarily through effects, so they are central to
the idea of writing shader programs. An effect file is a text file that contains the HLSL code
used by any number of vertex and pixel shaders.
An effect contains one or more techniques, which are in turn made up of at least one pass.
Each pass usually contains one vertex shader function, one pixel shader function, and any
number of render state and sampler state settings. In the next section, we’ll look as a simple
example effect and go over each line in detail.
Examining a Simple Effect
float4x4 mWorldViewProj;
// World * View * Projection transformation
float4 Vertex_Shader_Transform(
in float4 vPosition : POSITION ) : POSITION
{
float4 TransformedPosition;
// Transform the vertex into projection space.
TransformedPosition = mul( vPosition, mWorldViewProj );
return TransformedPosition;
}
float4 Pixel_Shader() : COLOR0
{
return float4(1,1,1,1);
}
technique ColorShaded
{
pass P0
{
VertexShader = compile vs_1_1 Vertex_Shader_Transform();
PixelShader = compile ps_1_4 Pixel_Shader();
}
}
This effect is one of the simplest effects that will produce a useable render. This shader will
take a world-view-projection matrix and render white geometry based on its vertex positions.
We’ll now break this shader down and explain each part in detail.
7
HLSL Semantics
In the code listing above, a syntax that may be somewhat unfamiliar are the capitalized
keywords that follow a variable and a colon. Consider the following line of HLSL code:
in float4 vPosition : POSITION
The POSITION keyword is called a semantic, which has an important place in HLSL code.
These keywords indicate to the shader compiler how to map the inputs and outputs of the
graphics data to the shader variables. In this example, vertex position data is being mapped to
an argument called vPosition. This informs the shader that the vPosition argument will
contain position data from the vertex buffer.
In this document we’ll explain the usage of semantics as they come up in the effect code.
HLSL Types
float4 TransformedPosition;
One aspect of HLSL programming that will quickly become intuitive is the different
primitive types available when initializing variables. In this case, a float4x4 primitive is used,
indicating a matrix of four floats by four floats. A Vector3, which is a structure of three
floats, is a float3 in HLSL.
The following is a table mapping some basic HLSL types to their .NET or XNA Framework
equivalents.
HLSL Type
XNA or .NET Framework Type
Float
Float
float2
Vector2
float3
Vector3
float4
Vector4, Quaternion, Color
float4x4
Matrix
Int
Int32
8
Effect Parameters
Effect parameters are the uniform data that remains constant for every vertex or pixel
processed by the Draw call. These can be initialized in the effect, though many times it’s
only appropriate to set these values in the render loop. Effect constants are used to represent a
variety of things, but most commonly they’ll represent transformation data, light settings, and
material information.
float4x4 mWorldViewProj;
// World * View * Projection transformation
Only one constant has been specified in the example effect. In this case, it’s the world-viewprojection matrix used to transform the vertices drawn from object space into clip space.
By itself, this uninitialized parameter isn’t all that helpful. The application must provide this
data. The XNA Framework API facilitates this assignment using the EffectParameter type,
which is used to get or set the value of the parameter in the effect. The following condensed
example shows how one might set the above matrix in C# code.
//Initialize the parameter
Effect exampleEffect = content.Load<Effect>("ExampleEffect");
EffectParameter worldViewProjParameter =
exampleEffect.Parameters["mWorldViewProj"];
Matrix worldViewProj = Matrix.Identity *
Matrix.CreateLookAt(
//world transform
//view transform
new Vector3(0f, 0f, -10f),
Vector3.Zero,
Vector3.Up) *
Matrix.CreatePerspectiveFieldOfView(
//projection transform
MathHelper.PiOver4,
1.333f,
0.1f,
100f);
//Set the world-view-projection matrix
worldViewProjParameter.SetValue(worldViewProj);
9
Uniform and Varying Inputs
The data that makes shaders function comes in two types: varying and uniform. Varying data
is unique to each execution of the shader function. In the case of vertex shaders, it’s the data
that comes from the vertex buffer. For pixel shaders, it is the data specific to the individual
pixel being rendered.
The other type of data is uniform, and it includes data that applies across the entire draw call.
This is also referred to as constant data, and is treated differently. The developer can set the
values of any of the shader constants through the Effect API. In the previous example, one of
the constants was a float4x4 (a 4x4 matrix of floating-point values) called mWorldViewProj.
In the XNA Framework API, the developer can look up the wvp field by name and set it to a
matrix available in the application. In this example, the matrix being set is the word-viewprojection matrix information required by nearly every basic vertex shader.
10
Shader functions
Vertex Shader Function
Vertex shaders take a variety of inputs, and the values of these inputs vary for each vertex
rendered. Usually, there’s a one-to-one correspondence between vertex shader inputs and the
structure of the vertices in the supplied vertex buffer.
float4 Vertex_Shader_Transform(
in float4 vPosition : POSITION ) : POSITION
In the provided example shader, the vertex shader takes a single input: the untransformed
vertex position. The way that the shader informs Direct3D what the purpose of each variable
is through semantics. In this case, the POSITION semantic is applied to vPosition, meaning
that vPosition will correspond to the x, y, and z-coordinates of a vertex.
There is a second POSITION semantic declared after the function declaration. This semantic
applies to the float4 return value of the vertex shader function. This is an output semantic that
informs the effect compiler that the return value is a transformed position.
Next, the body of the vertex shader function will be examined, starting with the first line:
float4 TransformedPosition;
Here, we’re initializing a variable that will hold the results of the vertex shader. This is a
structure of the type float4. The syntax for declaring a local variable is similar to variable
initialization in C# or other C-style languages.
In the fixed-function pipeline, the actual transformation function was hidden from the
developer. In the programmable pipeline (transformation pipeline), shader flexibility is
contingent on allowing the developer to apply transforms as needed.
In this example, the vertex shader is responsible for transforming the incoming vertex data.
This requires a calculation in the shader that multiplies a position vector by a world-viewprojection matrix.
// Transform the vertex into projection space.
TransformedPosition = mul( vPosition, mWorldViewProj );
This calculation transforms the vertex position from model space to projection space. These
transformed positions are used by the geometry processing portion of the Direct3D pipeline
to define the triangles that make up primitives on the screen. This is a matter of a simple
multiply (the mul function in HLSL). That function in the shader is identical to calling
Vector4.Transform(vPosition, mWorldViewProj) in the XNA Framework.
The last part of the vertex shader function simply returns the output from the shader. Like
C++ and C#, the return keyword is used to return the vertex shader outputs.
return TransformedPosition;
11
Pixel Shader Function
float4 Pixel_Shader( ) : COLOR0
The first thing to note is that the pixel shader is returning a float4 value. This value represents
the color of the pixel after the draw call. A pixel shader’s primary function is to return the
color of the current pixel. Like the vertex shader, a semantic (COLOR0) is defined for the
return value of the function.
Most simple pixel shader functions will only ever return an RGBA color. In most shaders,
color values are represented by floating-point vectors with 0.0 being completely dark and 1.0
as the maximum or “fully-on” state. The graphics hardware then translates this value into a
color that is meaningful in the context of the current back-buffer format.
return float4(1,1,1,1);
There’s not much to this pixel shader, since the vertex shader has done all the hard. The pixel
shader simply returns a white color. This means that all of the triangles drawn with this
shader will appear flat-white.
12
State Setting
The last part of the effect is used to set state on the GraphicsDevice. It tells the device how
the shader functions should be used.
technique ColorShaded
{
pass P0
{
VertexShader = compile vs_1_0 Vertex_Shader_Transform();
PixelShader = compile ps_1_4 Pixel_Shader();
}
}
This section informs the effect of which shaders to apply using a given technique or pass. An
effect file may contain several techniques. However, for this example, the effect is limited to
a single technique. Passes are included to allow multiple-pass renders, which are common in
more complex shaders. In this example, “P0” refers to the name of the pass.
There are only two states being set in this technique – the pixel shader and the vertex shader.
The compile command also indicates what shader model to which to compile the shader. For
now, it’s best not to get bogged down by shader model specifics. The samples all use
appropriate shader models for the techniques being employed.
There are lots of other states that can be set in the technique. For example, nearly all of the
render states and sampler states available on the GraphicsDevice can be set in the technique
code. This is a useful way to organize specific states with their accompanying shaders.
13
Example: Vertex lighting
Now we’ll take a look at a few vertex lighting effects (named FlatShaded and
VertexLighting) that are used in the code sample accompanying this document.
As this code is official sample code, made for learning more about shaders in XNA, from an
official XNA website (http://creators.xna.com/), the code is structured in a learning friendly
way. Throughout the code, you can find several “Example X.X” comments, indicating that
section is referred to in this document.
The controls in while running the sample (in XNA Game Studio Express):
14
Using an effect in an XNA game
As mentioned before, in this example there are 2 effects that are implemented, which are
named: “FlatShading” and “VertexLighting”. Each effect has its own file with the same name
and the extension “.fx”.
Example 1.1 shows the declaration of several effect types which are used throughout the
sample code (interestingly, there is also an ‘effect type’ named “noLightingEffect”), and in
example 1.2 these types are initialized.
To be able to use effects, a way is needed to provide data to them. These data fields are called
effect parameters and correspond directly to variables in the code.
This is why in Example 1.3, the world, view, and projection parameters are loaded by
referring to the strings "world," "view," and "projection."
These same variables are used in Example 2.1 in the FlatShaded.fx file at a global scope.
They represent the data that the shader needs to correctly position the vertices on the screen.
There's something interesting about the world, view, and projection parameters: they're
shared between all of the shaders in the example. When the Content Pipeline loads effects, it
puts them all in a global EffectPool. Shader parameters that have the same name and use the
shared keyword can be shared across multiple shaders, which is why the same parameters can
be found in VertexLighting.fx too.
The next thing to examine is where those effect parameters are set. In VertexLighting.cs
Example 1.4 and Example 1.5, we're using SetValue to set the effect parameter to a value in
the application. SetValue has several overloads to allow multiple kinds of data to be set.
However, it is the programmer’s responsibility to ensure that the type being set is the same
type of data in the effect code. For example, the world parameter is a 4×4 Matrix type in the
XNA Framework. In the HLSL effect code, a 4×4 Matrix is called a float4x4. Similarly, a
Vector3 in the XNA Framework is a float3 in HLSL.
The last interesting thing to look at in this part of the source code, deals with how we use the
effect to draw primitives to the screen. Example 1.6 in the source code describes this in detail,
but these are the general steps:
1 Set up the geometry.
The GraphicsDevice vertex stream, vertex declaration, and the indices are all set to the
correct values in this step.
2 Begin the effect.
Calling the Effect.Begin and Pass.Begin functions, which are used to be able to set different
GraphicsDevice states.
3 Draw the primitives.
4 End the effect.
Using the Pass.End and Effect.End functions to end the effect and the pass.
15
Flatshaded Effect
The FlatShaded effect consists of a simple vertex and pixel shader pair.
Example 2.1 contains the data supplied via EffectParameter objects.
Example 2.2 is the function body for the vertex shader function that positions the mesh
vertices on the screen. When the mesh is drawn, this function is run once for each vertex in
the scene. Each time the vertex shader function is run, the untransformed position parameter
is transformed into a transformed position returned at the end of the function.
This simple shader has only three lines of code. The first line combines the world, view, and
projection matrices into a single matrix that applies all three transformations.
The untransformed position parameter is then cast to a 4-component vector (with w equal to
1.0) and multiplied by the combined matrix.
The keyword mul is also known as an HLSL intrinsic function. In this case, the function takes
two matrix parameters and returns their product.
Most HLSL intrinsic functions are heavily overloaded for maximum flexibility though, and
mul is not an exception. For example, in Example 2.4 the mul function takes a 4-component
vector and a matrix. It is however safe to say conclude that the mul function always
multiplies its supplied parameters (if they are of valid type combinations).
The next function is the pixel shader function (Example 2.5), which is executed for each pixel
covered by the transformed geometry.
In most cases, the pixel shader function returns a 4-component vector representing the output
color. Because there is no need for any additional information, this function has no
parameters. This shader simply returns a white color, represented in floating-point RGBA
values as (1.0, 1.0, 1.0, 1.0).
The last section in the FlatShaded.fx file (Example 2.6) is the code block specific to an effect
file. XNA effect files differ slightly from straight HLSL because they define state for the 3D
device. In this shader, the state section defines a technique and a pass, which correspond to
the techniques and passes in the source code (Example 1.6). States that can be done on the
device are replicated for effect files to simplify development.
In the case of this effect, the pass P0 defines the VertexShader state and the PixelShader state
for the device when the pass is begun.
VertexShader is a keyword that represents the vertex shader on the graphics device. It is
assigned to the vertex shader defined above. However, there are two special keywords
exclusive to this state. The compile keyword is followed by vs_2_0. This indicates the shader
model to which to compile the function (in this case Vertex Shader Model 2.0).
The PixelShader state is set the same way as the VertexShader state, but using the ps_2_0
keyword to indicate that a pixel shader is being compiled.
16
VertexLighting Effect
The vertex lighting effect has a few more effect parameters specific to the more complex
effect. The lightColor and lightDirection parameters indicate the color and direction of the
global light illuminating the geometry. There is also a definition of an ambient light color
(Example 3.2) that represents a constant light scattered throughout the scene. Ambient light is
not directional, so only the color parameter is required.
To simplify the shader code, the effect defines a struct containing parameter information
(Example 3.3). The VertexShaderOutput structure contains fields with semantics, which is a
convenient way to clean up the function definition. Another noticeable thing is that struct
definitions in HLSL are terminated with a semicolon, which is a bit different than C#.
This new structure represents the data to be returned from the vertex shader. This time, the
shader will return both the required transformed position and the new COLOR0 semantic,
representing a color at that vertex.
The pixel shader now requires an input color to indicate what color to shade the destination
pixels. A second structure is defined in Example 3.4 with the input color. All the lighting
calculations are done in the vertex shader; the pixel shader simply returns the incoming color.
Example 3.5 is the vertex shader function. Most of this is identical to FlatShaded.fx, but there
are two new additions.
First, there's the new parameter, normal, which indicates the unit normal direction of the
vertex. A unit normal direction is required for the diffuse lighting equation.
The other new feature is that the function initializes an instance of the VertexShaderOutput
structure.
Examples 3.6–3.8 are the math equations used to calculate a diffuse color for the vertex. A
more complete discussion of this calculation is found in the next section of this document.
The addition in Example 3.8 adds the global ambient color to the diffuse color calculated for
the vertex. Since this sample doesn't account for transparency effects, the alpha component
value is fixed at 1.0. The individual components of a vector are accessible via RGBA or
XYZW.
The pixel shader function is slightly more complicated than the function in FlatShaded.fx,
since it returns the input color instead of simply returning white. This input color value is the
interpolated value of the color at the pixel.
The interpolation of color values happens between the end of the vertex shader and the start
of the pixel shader. When the triangles that make up a scene are set up from their constituent
vertices, the 3D device translates the triangle positions to pixels. The color data returned from
the vertex data is sent to the pixel shader interpolated with respect to the pixel's position
between the vertices that define the triangle.
17
Lambertian lighting explained
The lighting technique used in the vertex shader function in VertexLighting.fx is called
Lambertian lighting and represents the simplest way to calculate directional light.
Lambertian lighting always has the same intensity, no matter the distance of the light source.
When the light hits the surface, the amount of light reflected is calculated by the angle of
incidence the light has on the surface. When light has an angle of incidence of 90 degrees
(perpendicular) on a surface, it reflects all the light back with maximum intensity. However,
as the angle of incidence of the light is increased, the intensity of the light fades.
To calculate the intensity that a light has on a surface, the angle between the light direction
and the normal of the surface is measured, which is defined as a vector perpendicular to the
surface. One can measure this angle by using a dot product, which returns the projection of
the light direction vector onto the normal.
The dot intrinsic is one of the most fundamental operations in 3D rendering.
The dot product of two unit direction vectors yields the angle between them; the wider the
angle, the less intense the light. Therefore, the dot product of the normal and the light vector
gives us the light intensity at that vertex.
The light source used in the sample is only an approximation of directional lighting. The
vector that describes the light source determines the direction of the light. Since it's an
approximation, no matter where an object is, the direction in which the light shines toward it
is the same (similar to beams of sunlight in the real world). In addition, the intensity of the
light on individual objects is not taken into consideration.
Example 3.6 orients the normal direction into world space. This is done because the light
direction is defined in world coordinate space, but the normal is still in model space. For the
equation to make sense, both the normal and the light vector must be in the same coordinate
space.
Example 3.7 is the implementation of the dot-product function described above. The dot
intrinsic speaks for itself: it returns the scalar dot product of two vectors. The saturate
18
intrinsic is something new however. It clamps the value of the parameter between 0.0 and 1.0.
This prevents the intensity of the light from becoming negative for normals that face away
from the light source, resulting in physically impossible negative intensities.
Example 3.8 calculates the diffuse color by multiplying the scalar intensity by the light's
color.
19
Conclusion
Shaders have slowly evolved from a handy, but complex and limited, set of dynamic visual
effects, to an almost indispensable aspect of visually complex 2D and 3D programs
(especially games). This change can be explained in three points.
 The fact that basic shader programming followed the trend of becoming ‘higher level’
(more intuitive and less complex).
 The potential number of different shader effects gradually increased as hardware
became more powerful and new shader models were introduced.
 A large part of the popularity of shaders in programming stems from the fact that once
the effect has been programmed, it can be applied on any texture to give models or
environments a visually similar, and dynamic (i.e. not bland) look.
Although basic shader programming has become significantly easier compared to the first
years, it should be noted that there are some complex shader effects that take advantage of
features of new shader models.
We can conclude that shaders are an essential tool to create convincing, dynamic visual styles
that can be applied on any texture. With each shader model adding more features and
potential to shader programming, it’s safe to say that shaders will only become an even more
integral part in (visually complex) game programming in the coming years.
20
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