The shaders compile (I have confirmed this by purposefully making the GLSL code error). In addition, the program is created and linked correctly, as I have checked by printing the value of program and it was non-zero. However, I am still faced with a blue window (from glClearColor), and not a red one, as I… Read More GLSL Fragment Shader not modifying output colour

Initially I was using just gl_FragCoord.x which works great up to a point. However the range of gl_FragCoord.xy is between 0.5 and 1023.5, so after 1023.5 x just returns the same value. I have a uniform with the actual canvas size. uniform vec2 resolution; void main(void) { float pixelXPos = ? } Assuming the width… Read More In GLSL (WebGL), how can I get the screen pixel X position in the fragment shader?

I have a basic opengl app which is displaying a square, the squares colour is determined using interpolation. In my fragment shader I am trying to detect if the pixel runs along one of the edges of the square and if so to colour it black. This is my vertex shader. #version 330 layout (location… Read More Opengl shader to colour edges of square

I would like to achieve something like this : However, I fail to get the Y coordinates (before projection) of a given point inside the Fragment Shader. Here is my Fragment Shader : precision mediump float; vec4 blue = vec4(0.0, 0.0, 1.0, 1.0); vec4 pink = vec4(1.0, 0.0, 1.0, 1.0); void main() { float y_coordinates… Read More How to vary the color according to the elevation?