hmm, sometimes writing emails brings new ideas. I replaced the two floats with one vec2 pass_other and that works. marius.
uniform sampler2D texture; varying vec2 texcoord0; uniform vec4 hithresh; // hi and lo threshold uniform vec4 lothresh; uniform vec2 pass_other;
void main() { vec4 A = texture2D(texture, texcoord0); A.a = pass_other[0]; if ((A.r >= hithresh.r) || (A.r <= lothresh.r)) { A.a = pass_other[1]; } gl_FragColor = A;
}
marius schebella wrote:
hi, is it possible to ask shader related questions on the pd list? I am trying to write pix_alpha as a shader, but for now I have problems with the glsl code. (maybe you can also point me to a shader forum or mailing list that you know is good?) I have a fragment shader, which is not working, and I don't know why. the problem is that "A.a = other" does not set the value correct (it always sets 0). If I write A.a = 0.5 for example, then it is working. The variables are passed correctly, all other variables work too, so I think it is really a problem of how glsl works, and an error in the code. what it should do is when the red pixel value is within a certain range, the alpha value should be set to the pass value, and if it is outside, it should be set to the other value. (similar to pix_alpha, but only with red at the moment) thanks, marius.
// red pix alpha
uniform sampler2D texture; varying vec2 texcoord0;
uniform vec4 hithresh; // hi and lo threshold uniform vec4 lothresh; uniform float pass; uniform float other;
void main() { vec4 A = texture2D(texture, texcoord0); A.a = pass; if ((A.r >= hithresh.r) || (A.r <= lothresh.r)) { A.a = other; } gl_FragColor = A; }