Check if sampler2D is empty
Here below the 2 versions, with and without if... else...
conditional statement. The conditional statement avoids to have to sample the texture if not used.
The uniform int textureSample
is set to 1 or 0 for the texture or the color to show up respectively. Both uniform variables are normally set up by the program, not the shader.
uniform int textureSample = 1;
uniform vec3 color = vec3(1.0, 1.0, 0.0);
void main() { // without if... else...
// ...
vec3 materialDiffuseColor = textureSample * texture( textureSampler, fragmentTexture ).rgb - (textureSample - 1) * color;
// ...
}
void main() { // with if... else...
// ...
if (textureSample == 1) { // 1 if texture, 0 if color
vec3 materialDiffuseColor = textureSample * texture( textureSampler, fragmentTexture ).rgb;
vec3 materialAmbientColor = vec3(0.5, 0.5, 0.5) * materialDiffuseColor;
vec3 materialSpecularColor = vec3(0.3, 0.3, 0.3);
gl_Color = brightness *
(materialAmbientColor +
materialDiffuseColor * lightPowerColor * cosTheta / distanceLight2 +
materialSpecularColor * lightPowerColor * pow(cosAlpha, 10000) / distanceLight2);
}
else {
vec3 materialDiffuseColor = color;
vec3 materialAmbientColor = vec3(0.5, 0.5, 0.5) * materialDiffuseColor;
vec3 materialSpecularColor = vec3(0.3, 0.3, 0.3);
gl_Color = brightness *
(materialAmbientColor +
materialDiffuseColor * lightPowerColor * cosTheta / distanceLight2 +
materialSpecularColor * lightPowerColor * pow(cosAlpha, 10000) / distanceLight2);
}
// ...
}
A sampler cannot be "empty". A valid texture must be bound to the texture units referenced by each sampler in order for rendering to have well-defined behavior.
But that doesn't mean you have to read from the texture that's bound there. It's perfectly valid to use a uniform
value to tell the shader whether to read from the texture or not.
But you still have to bind a simple, 1x1 texture there. Indeed, you can use textureSize
on the sampler; if it is a 1x1 texture, then don't bother to read from it. Note that this might be slower than using a uniform
.