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So I've got a triangle:
And I've got a vertex shader:
uniform mat4 uViewProjection;
attribute vec3 aVertexPosition;
attribute vec2 aTextureCoords;
varying vec2 vTextureCoords;
void main(void) {
vTextureCoords = aTextureCoords;
gl_Position = uViewProjection * vec4(aVertexPosition, 1.0);
}
And I've got a fragment shader:
precision mediump float;
uniform sampler2D uMyTexture;
varying vec2 vTextureCoords;
void main(void) {
gl_FragColor = texture2D(uMyTexture, vTextureCoords);
}
And I feed in three sets of vertices and UVs, interleaved:
# x, y, z, s, t
0.0, 1.0, 0.0, 0.5, 1.0
-1.0, -1.0, 0.0, 0.0, 0.0
1.0, -1.0, 0.0, 1.0, 0.0
How does the fragment shader know to draw pixel A differently from pixel B? What changes?
443
A Fragment Shader is the Shader stage that will process a Fragment generated by the Rasterization into a set of colors and a single depth value. The fragment shader is the OpenGL pipeline stage after a primitive is rasterized. For each sample of the pixels covered by a primitive, a "fragment" is generated.
A fragment shader is the same as pixel shader.
A texture is an OpenGL Object that contains one or more images that all have the same image format. A texture can be used in two ways: it can be the source of a texture access from a Shader, or it can be used as a render target.
A Shader is a user-defined program designed to run on some stage of a graphics processor. Shaders provide the code for certain programmable stages of the rendering pipeline. They can also be used in a slightly more limited form for general, on-GPU computation.
As I understand it the rasterization stage of the GL pipeline interpolates vTextureCoords across the triangle face, running the fragment shader on each pixel with the interpolated value.
191
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