Fragment Shader

Simple Astroids clone

Published Nov 14, 2017

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If you noticed any problems with black being drawn on top of sprites, that is because transparent fragments aren’t being discarded. This step is just a quick change to the fragment shader to fix this problem.

shader/fragment.glsl

#version 120

varying vec2 texcoord;
uniform sampler2D mytexture;

void main(void) {

    vec2 flipped_texcoord = vec2(texcoord.x, 1.0 - texcoord.y);
    vec4 frag = texture2D(mytexture, flipped_texcoord);
    
    if(frag.z == 0) {
        discard;
    }
    
    gl_FragColor = frag;

}

Compile

Since our shader code is compiled by our program, there’s no need to recompile. But just to have as a reference, compile command is below.

$ gcc -c -o DashGL/dashgl.o DashGL/dashgl.c -lepoxy -lpng -lm
$ gcc `pkg-config --cflags gtk+-3.0` main.c DashGL/dashgl.o `pkg-config --libs gtk+-3.0` \
-lepoxy -lm -lpng

Run

$ ./a.out