Trouble with shader

Programming Questions

timur2008m

in Programming Questions • 9 months ago

Hello I found my desired shader shader http://glsl.heroku.com/e # 5604,6 and tried to use it in my sketch, but it does not work. I can not understand what I'm doing wrong, please tell me what I'm doing wrong: ((

#ifdef GL_ES
precision mediump float;
precision mediump int;
#endif
uniform float time;
uniform vec2 mouse;
uniform vec2 resolution;
void main( void ) {
vec2 position = gl_FragCoord.xy;
float color;
vec2 lightpos = mouse*resolution;
vec2 norm = lightpos - position;
float sdist = pow((norm.x * norm.x),1.0/3.0) + pow((norm.y * norm.y),1.0/3.0);
vec3 light_color = vec3(1.2,0.8,0.6);
color = (1.0 / (sdist * (mouse.x)))*cos(0.7*(sin(time*1.0)));
gl_FragColor = vec4(color,color,color,1.0)*vec4(light_color,1.0);
}

This my scetch:

PShader shine;
void setup()
{
size(1024,768,P2D);
shine = loadShader("shine.glsl");
shine.set("resolution",float(width),float(height));
}
void draw(){
shine.set("mouse",float(mouseX),float(mouseY));
shine.set("time",millis()/1000.0);
shader(shine);
}

Replies(2)

andres

Re: Trouble with shader

9 months ago

The shader needs some geometry to work on, in this case a rect covering the entire viewport so each pixel goes trough the shader. In addition, 2.0b7 detects the presence of uniforms called resolution, mouse and time in the glsl source code and sets the appropriate values automatically, so you don't need to do it explicitly in the sketch (however, this functionality is still not set in stone, so might change in the next release). So the following sketch code should work:

PShader shine;
void setup() {
size(400,400,P2D);
shine = loadShader("shine.glsl");
}
void draw() {
shader(shine);
rect(0, 0, width, height);
}

I think that the math in the fragment shader expects normalized fragment and mouse positions, so:

uniform float time;
uniform vec2 mouse;
uniform vec2 resolution;
void main( void ) {
vec2 position = gl_FragCoord.xy / resolution;
float color;
vec2 lightpos = mouse / resolution;
vec2 norm = lightpos - position;
float sdist = pow((norm.x * norm.x),1.0/3.0) + pow((norm.y * norm.y),1.0/3.0);
vec3 light_color = vec3(1.2,0.8,0.6);
color = (1.0 / (sdist * (mouse.x)))*cos(0.7*(sin(time*1.0)));
gl_FragColor = vec4(color,color,color,1.0)*vec4(light_color,1.0);
}

Note gl_FragCoord.xy / resolution and mouse / resolution, which do the normalizations.

timur2008m

Re: Trouble with shader

9 months ago

Thanks