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iosopengl-esvertex-shader

OpenGL ES: Pass single float to vertex shader?

I'm trying to pass a single float to my vertex shader so I can set gl_PointSize to be that float. However, it's not working and I think it's due to me using glVertexAttribPointer:

glVertexAttribPointer(1, 1, GLenum(GL_FLOAT), GLboolean(GL_FALSE), GLsizei(MemoryLayout<Vertex>.size), BUFFER_OFFSET(2 * MemoryLayout<Float>.size))

I need the buffer offset since I'm also setting the position using glVertexAttribPointer before that using this:

glVertexAttribPointer(0, 2, GLenum(GL_FLOAT), GLboolean(GL_FALSE), GLsizei(MemoryLayout<Vertex>.size), BUFFER_OFFSET(0))

This is my vertex structure:

struct Vertex {
  var x, y, size: Float
}

This is the vertex shader:

attribute vec4 Position;
attribute float Size; // I tried vec4, no luck

void main(void) {
  gl_PointSize = Size;
  gl_Position = Position;
}
Solution

  • Reto Koradi had the answer! You need to call glBindAttribLocation beforehand when compiling the shader to bind it correctly.