Having some issues with a geometry shader in a very basic DX app.
We have an assignment where we are supposed to render a rotating textured quad, and in the geometry shader duplicate this quad and offset it by its normal. Very basic stuff essentially.
My issue is that the duplicated quad, when rendered in front of the original quad, seems to fail the Z test and thus the original quad is rendered on top of it.
Whats even weirder is that this only happens for one of the triangles in the duplicated quad, against one of the original quads triangles.
Here's a video to show you what happens: Video (ignore the stretched textures)
Here's my GS: (VS is simple passthrough shader and PS is just as basic)
struct VS_OUT
{
float4 Pos : SV_POSITION;
float2 UV : TEXCOORD;
};
struct VS_IN
{
float4 Pos : POSITION;
float2 UV : TEXCOORD;
};
cbuffer cbPerObject : register(b0)
{
float4x4 WVP;
};
[maxvertexcount(6)]
void main(
triangle VS_IN input[3],
inout TriangleStream< VS_OUT > output
)
{
//Calculate normal
float4 faceEdgeA = input[1].Pos - input[0].Pos;
float4 faceEdgeB = input[2].Pos - input[0].Pos;
float3 faceNormal = normalize(cross(faceEdgeA.xyz, faceEdgeB.xyz));
//Input triangle, transformed
for (uint i = 0; i < 3; i++)
{
VS_OUT element;
VS_IN vert = input[i];
element.Pos = mul(vert.Pos, WVP);
element.UV = vert.UV;
output.Append(element);
}
output.RestartStrip();
for (uint j = 0; j < 3; j++)
{
VS_OUT element;
VS_IN vert = input[j];
element.Pos = mul(vert.Pos + float4(faceNormal, 0.0f), WVP);
element.Pos.xyz;
element.UV = vert.UV;
output.Append(element);
}
}
I havent used geometry shaders much so im not 100% on what happens behind the scenes.
Any tips appreciated!
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