Master's Thesis - Studierstube Augmented Reality Project - Graz ...

4.4 Visualization Framework
3 void main ( void )
4 {
5 // Texture coordinate of the vertex
6 gl_TexCoord [0] = gl_MultiTexCoord0 ;
7 // Position of the vertex
8 gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex ;
9 }
10
11
12 [ Fragment shader ]
13 uniform sampler2D aTexture ; // an arbitrary input texture
14
15 void main ( void )
16 {
17 // read the RGBA color of the texture ’s pixel
18 // at an interpolated texture position
19 vec4 texVec = texture2D ( aTexture , vec2 ( gl_TexCoord [0]));
20 // set the color of the rendered fragment
21 gl_FragColor = texVec ;
22 }
Available data-types
• Standard types: Besides bool, int and float, also vector types like vec2, vec3
or vec4 and matrix types like mat2, mat3 or mat4 and similar are available.
• Textures: defined with sampler1D, sampler2D or sampler3D (and even some
more for cube- or shadow maps) and accessed via the built-in functions texture1D, texture2D
or texture3D...
• Arrays: defined in the same way as in C with square brackets.
• Type qualifiers: Referring to the two most frequently used, uniform defines a
variable set by the OpenGL API and varying a variable which is interpolated
between vertex and fragment shader and therefore accessible in both.
built-in functions and values
• Vector and matrix types can be accessed element wise via a swizzle operator.
For example a four dimensional vector accessed with vector.xyz or vector.rgb
will result in the first three elements. (w or a refers to the fourth component).
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