Graphics Reference
In-Depth Information
This code might result in each reference to the literal values 0, 1, 0.0, and
1.0 counting against the uniform storage. To guarantee that these literal
values count only once against the uniform storage, the vertex shader
code snippet should be written as follows:
#version 300 es
#define NUM_TEXTURES 2
const int c_zero = 0;
const int c_one = 1;
uniform mat4 tex_matrix[NUM_TEXTURES]; // texture
// matrices
uniform bool enable_tex[NUM_TEXTURES]; // texture
// enables
uniform bool enable_tex_matrix[NUM_TEXTURES]; // texture matrix
// enables
in vec4 a_texcoord0; // available if enable_tex[0] is true
in vec4 a_texcoordl; // available if enable_tex[1] is true
out vec4 v_texcoord[NUM_TEXTURES];
void main()
{
v_texcoord[c_zero] = vec4 ( float(c_zero), float(c_zero),
float(c_zero), float(c_one) );
// is texture 0 enabled
if ( enable_tex[c_zero] )
{
// is texture matrix 0 enabled
if ( enable_tex_matrix[c_zero] )
v_texcoord[c_zero] = tex_matrix[c_zero] * a_texcoord0;
else
v_texcoord[c_zero] = a_texcoord0;
}
v_texcoord[c_one] = vec4(float(c_zero), float(c_zero),
float(c_zero), float(c_one));
// is texture 1 enabled
if ( enable_tex[c_one] )
{
// is texture matrix 1 enabled
if ( enable_tex_matrix[c_one] )
v_texcoord[c_one] = tex_matrix[c_one] * a_texcoordl;
else
v_texcoord[c_one] = a_texcoordl;
}
// set gl_Position to make this into a valid vertex shader
}
