2D Scaling Pixel Art Shader (Metal) - Passing Texture Size Into The Vertex Shader

2dpixelgamemacplatform.mm

// A simple struct representing the size of the texture in terms of
// texels.
typedef struct
{
    real32 Width;
    real32 Height;
} MacTextureSize;

// PRETEND THIS IS INSIDE OF A RENDERING FUNCTION

// An example of how you might pass this struct into MTLRenderEncoder
// while setting up a render pass. The specifics don't matter so much
// as the line where the texture size is passed in using setVertexBytes:
[RenderEncoder setFragmentTexture: [self GameCharacterTextureAtlas]
                                    atIndex: 0];
 
// This assumes a triple buffered setup where there are three vertex buffers
// and your renderer tracks the current frame.
id<MTLBuffer> VertexBuffer = [[self VertexBuffers] objectAtIndex: _currentFrameIndex];
[RenderEncoder setVertexBuffer: VertexBuffer offset: 0 atIndex: 0];

// If you use a 2D texture array, you will probably know this ahead of time.
// For example, my game character array has the game character at 32x32 texels/frame.
MacTextureSize TextureSize = {};
TextureSize.Width = 32;
TextureSize.Height = 32;
           
// The index you use is kind of arbitrary. If you pass other parameters into the
// vertex shader, it will depend on those. Mine uses two params before the texture
// size parameter.
[RenderEncoder setVertexBytes:&TextureSize                        
                       length:sizeof(TextureSize)                             
                      atIndex:2];                             
                         
// Do the rest of your drawing as normal.
[RenderEncoder drawPrimitives: MTLPrimitiveTypeTriangle                  
                  vertexStart: 0               
                  vertexCount: VertexCount];