[color=#4A4A4A]Okay, so I've set up a light pre-pass render system once before, except my new one is slightly different.[color=#4A4A4A]
I'm trying to implement it without using a normal buffer. In theory this would work well for the toon-shaded game I'm making, except I've run into a problem.
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When I render a pointlight (as a sphere) in the lighting pass, I'm sampling from the depth-map and comparing the sphere's depth.[color=#4A4A4A]
Clipping any pixels from drawing where the scene is closer to the camera then the light. This sadly only works for one side of the point-light

[font="'Segoe UI"][size="2"][color="#4a4a4a"]BTW: I'm using XNA, but that's irrelevant to this problem... [/font]

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VertexShaderOutput VertexShaderFunction(VertexShaderInput input)
{
VertexShaderOutput output;

float4 worldPosition = mul(input.Position, World);
float4 viewPosition = mul(worldPosition, View);
output.Position = mul(viewPosition, Projection);

output.Depth = 1 - (viewPosition.z / viewPosition.w);

return output;
}

float4 PixelShaderFunction(VertexShaderOutput input, float2 screenSpace : VPOS ) : COLOR0
{
screenSpace /= float2(1280, 720);

float depth = tex2D(Depth, screenSpace);

clip(depth < input.Depth ? -1:1);

return LightColor;
}

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When I render with this code, the clip function works as expected, but I don't know how to clip the sphere from lighting parts of the scene that are behind it, beyond it's reach.

Here's a pic showing that the depth behind the sphere isn't being taken into account:
The farthest cube shouldn't be receiving any light, and the plane shouldn't be shaded that mush in the rear.



Here's another picture showing the problem a bit more visibly. Top is the final image, bottom is the light buffer:




I think I'm just missing the last step for determining the influence the light has, but I just can't figure it out!
Any help would be greatly appreciated.

I think I'll try solution 1, but despite my efforts I've yet to find an example of calculating world position that works with my depth buffer...

[color=#000000]output[color=#666600].[color=#660066]Depth[color=#000000] [color=#666600]=[color=#000000] [color=#006666]1[color=#000000] [color=#666600]-[color=#000000] [color=#666600]([color=#000000]viewPosition[color=#666600].[color=#000000]z [color=#666600]/[color=#000000] viewPosition[color=#666600].[color=#000000]w[color=#666600]);

I like the way I'm calculating Depth right now, as it returns a linear value from the camera, is there any way I can calculate the world position using this type of depth?

Thanks, I got it!

Here's the code if anyone else runs into this problem:

Depth is now : Output.Position.z / Output.Position.w


screenSpace /= float2(1279.5, 719.5);
float lightDepth = input.Depth.x / input.Depth.y;
float sceneDepth = tex2D(Depth, screenSpace).r;
clip(sceneDepth > lightDepth || sceneDepth == 0 ? -1:1);
float4 H = float4(screenSpace.x * 2 - 1, (1 - screenSpace.y) * 2 - 1, sceneDepth, 1);
float4 D = mul(H, iViewProjection);
float4 worldPos = D / D.w;
clip( length(LightPosition - worldPos) > LightRadius ? -1:1);
return LightColor;


Pic: