Geometry shader worldviewprojection

Question

I'm writing a simple geometry shader to create 3D "primitives" in place of a single point. I am performing all of the world-view-projection conversions within the geometry shader after creating the triangle strips to form the 3D primitive. Unfortunately, it seems to be creating the triangles in projection space, and giving me incorrect results. The following pictures demonstrate this problem. Any advice on how to work around this problem?

As can be seen here, the second top face seems to be rendered as if it was pulled off the top and splayed out.

Here is the geometry shader I am using, and a set of coordinates I use to generate these faces

static float3 cube_coords[8] =
{

float3(1, -1, 1),
float3(-1, -1, 1),
float3(1, 1, 1),
float3(-1, 1, 1),

float3(1, 1, 1),
float3(-1, 1, 1),
float3(1, 1, -1),
float3(-1, 1, -1),

};



[maxvertexcount(8)]
void GSMain(point GSInput input[1], inout TriangleStream< GSOutput > output)
{
GSOutput p;

for(unsigned int j = 0; j < 2; j++)
{
    for(unsigned int i = 0; i < 4; i++)
    {
        p.Pos = input[0].Pos;
        p.Pos += float4(cube_coords[i + (4*j)],1.0);
        p.Pos = mul(p.Pos, worldViewProjection);
        p.Color = input[0].Color;
        p.Light = input[0].Light;
        p.Norm = normals[j];
        output.Append(p);
    }
    output.RestartStrip();
}
}

Answer 1

I have encountered the answer to this question myself. I had simply made a mix-up involving column major vs row major matrices, and the order in which i was multiplying them against my position within the geometry shader.

Answer 2

Before going into geometry shader loop, coordinates you provide are not cube coordinates if it's what you are trying to achieve.

Your code:

float3(1, -1, 1),
float3(-1, -1, 1),
float3(1, 1, 1),
float3(-1, 1, 1),

float3(1, 1, 1),
float3(-1, 1, 1),
float3(1, 1, -1),
float3(-1, 1, -1),

5th point covers 3rd point and 6th point covers 4th point.

Edit: Sorry just realized I misunderstood the question.

Edit2: Not sure it's what causes the problem but vertex positions leaving the geometry shader must be transformed to homogeneous clip space. This is how it's usually done: (pseudocode)

struct VStoGS
{
   float3 position : POSITION;
   //other stuff
};

struct GStoPS
{
   float4 positionH : SV_POSITION; //for homogeneous clip space transform
   float3 positionW : POSITION; //for world space transform
   //other stuff
};

And in geometry shader:

foreachvertex
{
   gsOutput[i].positionW = mul(float4(vertex[i].pos, 1.0f), world).xyz;
   gsOutput[i].positionH = mul(float4(vertex[i].pos, 1.0f, worldViewProj);
   //other stuff
}

Edit3: positionW is only needed for extra stuff in PS so that's not it.