SpriteBatch Vertex Shader GLSL code

spritebatch.glsl

#version 330 core
layout (location = 0) in vec3 VertexPosition;
layout (location = 1) in vec2 VertexTexCoord;
layout (location = 2) in vec4 VertexColor;

int QuadIndexOffsets[6] = int[6](0, 1, 2, 2, 3, 0);
vec2 QuadCoords[6] = vec2[6](vec2(0.0, 0.0), vec2(1.0, 0.0), vec2(1.0, 1.0), vec2(1.0, 1.0), vec2(0.0, 1.0), vec2(0.0, 0.0));
uniform samplerBuffer VertexBuffer;

uniform mat4 ProjectionMatrix;
out vec2 VaryingTexCoord;
out vec4 VaryingColor;

void main()
{
    int QuadID = gl_VertexID / 6;
    int QuadVertexID = gl_VertexID - 6 * QuadID;
    int VertexID = QuadID * 4 + QuadIndexOffsets[QuadVertexID];
    
    int BufferIndex = QuadID * 2;
    vec4 Attributes0 = texelFetch(VertexBuffer, BufferIndex);
    vec4 Attributes1 = texelFetch(VertexBuffer, BufferIndex + 1);
    mat3x2 QuadTransform = mat3x2(Attributes0.xy, Attributes0.zw, Attributes1.xy);
    
    vec2 QuadCoord = QuadCoords[QuadVertexID];
    vec2 Position = QuadTransform * vec3(QuadCoord, 1.0);
    
    VaryingTexCoord = QuadCoord;
    VaryingColor = vec4(Attributes1.w);
    
    gl_Position = ProjectionMatrix * vec4(Position.xy, Attributes1.z, 1.0);
}