3 replies to this topic

[Vodáček]

Hi, I have almost half of a year problem with implementation projective texture in my Light Pre-Pass renderer. My projector don't affect albedo and is drawn in lighting pass. I have this projector View a Projection matrix:

Matrix projection = Matrix.CreateOrthographicOffCenter(-halfWidth * Scale, halfWidth * Scale, -halfHeight * Scale, halfHeight * Scale, -1000, 1000);
Matrix view = Matrix.CreateLookAt(Position, Target, Vector3.Up);

Where halfWidth and halfHeight is half texture width and height, Position is Projector position and target is projector target. This seems to be ok. I am drawing full screen quad with this shader:

float4x4 InvViewProjection;

texture2D DepthTexture;
texture2D NormalTexture;
texture2D ProjectorTexture;

float4x4 ProjectorViewProjection;

sampler2D depthSampler = sampler_state {
	texture = <DepthTexture>;
	minfilter = point;
	magfilter = point;
	mipfilter = point;
};

sampler2D normalSampler = sampler_state {
	texture = <NormalTexture>;
	minfilter = point;
	magfilter = point;
	mipfilter = point;
};

sampler2D projectorSampler = sampler_state {
	texture = <ProjectorTexture>;
	AddressU  = Clamp;
	AddressV  = Clamp;
};

float viewportWidth;
float viewportHeight;

// Calculate the 2D screen position of a 3D position
float2 postProjToScreen(float4 position) {
	float2 screenPos = position.xy / position.w;
	return 0.5f * (float2(screenPos.x, -screenPos.y) + 1);
}

// Calculate the size of one half of a pixel, to convert
// between texels and pixels
float2 halfPixel() {
	return 0.5f / float2(viewportWidth, viewportHeight);
}

struct VertexShaderInput {
	float4 Position : POSITION0;
};

struct VertexShaderOutput {
	float4 Position :POSITION0;
	float4 PositionCopy : TEXCOORD1;
};

VertexShaderOutput VertexShaderFunction(VertexShaderInput input) {
	VertexShaderOutput output;
	output.Position = input.Position;
	output.PositionCopy=output.Position;
	return output;
}

float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 {
	float2 texCoord =postProjToScreen(input.PositionCopy) + halfPixel();

	// Extract the depth for this pixel from the depth map
	float4 depth = tex2D(depthSampler, texCoord);
	//return float4(depth.r,0,0,1);
	// Recreate the position with the UV coordinates and depth value
	float4 position;
	position.x = texCoord.x * 2 - 1;
	position.y = (1 - texCoord.y) * 2 - 1;
	position.z = depth.r;
	position.w = 1.0f;

	// Transform position from screen space to world space
	position = mul(position, InvViewProjection);
	position.xyz /= position.w;
	//compute projection
	float3 projection=tex2D(projectorSampler,postProjToScreen(mul(position,ProjectorViewProjection)) + halfPixel());
	return float4(projection,1);
}

In first part of pixel shader is recovered position from G-buffer (this code I am using in other shaders without any problem) and then is tranformed to projector viewprojection space. Where is hidden my mistake? Thanks for advice and please be tolerant to my english.

[MJP]

What's the actual problem that you're experiencing?

[Vodáček]

Problem is that projection doesn't appear. Here is image of my situation:


Green lines are rendered projector frustum.

[Vodáček]

nobody haven't any ideas?