gistfile1.glsl

// Vertex
#version 150 core

uniform mat4 trans;

in vec2 pos;
in float id;
out mat4 projection;
out float gId;

void main() {
	gId = id;
	projection = gl_ModelViewProjectionMatrix*trans;
	gl_Position = projection*vec4(pos, 0.0, 1.0);
}

// Geometry
#version 150 core

uniform vec2 tileSize = vec2(16, 16);
uniform vec2 sheetSize = vec2(128, 128);

layout(points) in;
layout(triangle_strip, max_vertices = 6) out;

in mat4 projection [];								// Current world projection matrix
in float gId [];									// Tile sprite ID used to calculate texture coords
out vec2 fCoord;									// Output to fragment shader

void main() {
	float leng = sheetSize.x / tileSize.x;
	float col = mod(gId[0], leng)*tileSize.x/sheetSize.x;
	float row = floor(gId[0] / leng)*tileSize.y/sheetSize.y;

	vec2 ts = tileSize/sheetSize;

	// 0,0
	fCoord = vec2(col, row);
	gl_Position = gl_in[0].gl_Position + (projection[0]*vec4(0.0, 0.0, 0.0, 0.0));
    EmitVertex();

	// 1,0
	fCoord = vec2(col+ts.x, row);
    gl_Position = gl_in[0].gl_Position + (projection[0]*vec4(tileSize.x, 0.0, 0.0, 0.0));
    EmitVertex();

	// 1,1
	fCoord = vec2(col+ts.x, row+ts.y);
	gl_Position = gl_in[0].gl_Position + (projection[0]*vec4(tileSize.x, tileSize.y, 0.0, 0.0));
    EmitVertex();

	// 1,1
	fCoord = vec2(col+ts.x, row+ts.y);
	gl_Position = gl_in[0].gl_Position + (projection[0]*vec4(tileSize.x, tileSize.y, 0.0, 0.0));
    EmitVertex();

	// 0,1
	fCoord = vec2(col, row+ts.y);
	gl_Position = gl_in[0].gl_Position + (projection[0]*vec4(0.0, tileSize.y, 0.0, 0.0));
    EmitVertex();

	// 0,0
	fCoord = vec2(col, row);
	gl_Position = gl_in[0].gl_Position + (projection[0]*vec4(0.0, 0.0, 0.0, 0.0));
    EmitVertex();

    EndPrimitive();
}

// Fragment
#version 150 core

uniform sampler2D image;

in vec2 fCoord;
out vec4 outColor;

void main() {
	outColor = texture(image, fCoord);
}