Project 2D texture onto a cubemap

I think I was going about this the wrong way. I didn't need to do some unruly math to convert spherical coordinates into UV coordinates for all 6 faces, I just needed to project the quad properly.

I made a fragment shader that simply passes through the texture it's provided, and the texture coordinates are just a quad's UV's (with no alterations).

#version 430 core layout (location = 0) uniform sampler2D screenTexture; layout (location = 0) out vec3 OutputColor; in vec2 TexCoord; void main() { OutputColor = texture(screenTexture, UV).rgb; } 

Recall my goal: to project what the user sees into a cubemap.

In the vertex shader, I position the quad at the far plane of the user's frustum, and then render it from the perspective of each of the 6 viewing angles of the cubemap.

void main() { TexCoord = (vertex.xy + vec2(1.0)) / 2.0; // Strip the translation from the matrix mat4 InvRotVMatrix = vMatrix_Inverse; InvRotVMatrix[3][0] = 0; InvRotVMatrix[3][1] = 0; InvRotVMatrix[3][2] = 0; vec4 WorldPos = (InvRotVMatrix * pMatrix_Inverse * vec4(vertex.xyz, 1)); gl_Position = Proj * View[View_Index] * WorldPos; }