Hi,

I have Shadowmaps working based off of several tutorials around the internet, and have been able to get transparency working by discarding pixels in a texture that have an alpha value. But this only seems to work on only a single texture sampler which I pass to the shadowmap pixel shader.

I'm now trying to work out how I would get my shadows working irrespective of how many textures/models I have in a scene. I can't quite get my head around how I can do this. How have others managed to do this?

Cheers

6

Hi,

Can I bump this question please.

Thanks

6

Hmm, no anwser after 300+ views. I'm sure it's not that complicated so let me re-word the issue I have.

The depthmap texture, ( from the lights point-of-view), is created when my pixel shader receives the depth value of a fragment from a vertex shader. This is all very simple and creates a nice depthmap of my geometry.

Next, to create the shadowmap I have a pixelshader which compares the Projected depthMap with the depth from my current Viewposition and accordingly set the pixel as in light or in shadow.

The problem is, at some point, ( either at the creation of the depthMap or shadowMap), I would like to check if the texture fragment has an alpha channel value. I have been able to do this when I explicitly pass in a texture sampler to the pixel shader, but I don't know how to check for alpha values when there is an unknown number of textures to test.

So how do others do this? I'm just looking for a general direction to go in, not for specific code. Just out of interest, is it best to perform the alpha test when creating the depthMap or at the shadowMap stage.

Thanks

6

Ok, perhaps I have my terminology wrong. So it sounds like what you're saying is that the depth texture which tells me how far the lighting is reaching, is actually called the shadowMap. In other words the shadowMap actually stores light depth information. Kinda makes sense.

Now, where you say "If the alpha value of the object you are rendering at this time is below a certain threshold, discard it.". Yep, I understand that's what I need to do, but the shader is a post process shader so how to I access the texture/sampler belonging to that object? Do I need to declare the sampler at the beginning of the shader file? If so then what if I have 50 textures with alpha information?

Thanks

6

Sorry, I'm still confused. I've various different things, but nothing seems to be working.

At the point where I'm creating the ShadowMap ( aka depthmap) the vertex shader is passing all the vertex data including the depth information to the pixel shader. At the moment the pixel shader just stores the depth in a 'r32f' texture. Is it at this point I clip() any alpha values?

If so, I'm still not clear how I access the alpha value. I presume the Vertex Shader can't provide this info because it just processes vertices. Is there some semantic, ( like COLOR0) I need to use when I'm in the Pixel shader? I just can't find anything online about how to do this part :(

Here is a snippet of my code which shows a shadowMap texture being created, then it is used in ScreenShadOUT_PS as part of the camparison process

///////////////////////////////////////////////////////////
///////////////////////////// Connector Data Struct ///////
///////////////////////////////////////////////////////////

struct OneTexelVertex
 {
    float4 Position	: POSITION;
    float4 color	: COLOR0;
    float2 UV		: TEXCOORD0;
    float4 depth	: TEXCOORD1;
    float4 ViewPosition : TEXCOORD2;
    float4 normal   : NORMAL;	
};


///////////////////////////////////////////////////////////
////////////////////Pass = DepthMap ///////////////////////
///////////////////////////////////////////////////////////
// RTT available in this pass = ScnMap
OneTexelVertex ScreenIN_VS(OneTexelVertex IN) 
{
    OneTexelVertex OUT = (OneTexelVertex)0;
	OUT.Position = mul(IN.Position, gWorld);
	OUT.Position = mul(OUT.Position, gLightView);
	OUT.Position = mul(OUT.Position, gLightOrtho);
	
    OUT.UV = float2(IN.UV.xy + ViewportOffset);
	OUT.depth.x = OUT.Position.z/OUT.Position.w;
	OUT.normal = IN.normal;
    return OUT;
}
float4 ScreenOUT_PS(OneTexelVertex IN) : COLOR
{   
	float depthValue =  IN.depth.x;
	return float4(depthValue,depthValue,depthValue,1.0f);
} 

// RTT Output = ShadowMap
///////////////////////////////////////////////////////////
/////////////// Pass = Shadow /////////////////////////////
///////////////////////////////////////////////////////////
OneTexelVertex ScreenShadIN_VS(OneTexelVertex IN) 
{
    OneTexelVertex OUT = (OneTexelVertex)0;
    OUT.Position = mul(IN.Position, gWorldViewProjection);
	OUT.ViewPosition = mul(IN.Position, gWorld);
	OUT.ViewPosition = mul(OUT.ViewPosition, gLightView);
	OUT.ViewPosition = mul(OUT.ViewPosition, gLightOrtho);
	
    OUT.UV = float2(IN.UV.xy + ViewportOffset);
	OUT.normal = mul(IN.normal, gWorld);
	OUT.normal = normalize(OUT.normal);
    return OUT;
	
}

float4 ScreenShadOUT_PS(OneTexelVertex IN) : COLOR
{
	float depthValue;
	float4 color;
	float3 lightDir;
	float lightIntensity;
	float4 textureColor;
	float2 projectTexCoord;
	float4 projectionColor;	
	color = float4(0.5,0.5,0.5,1);
	lightDir = -gLightDirection;
	lightIntensity = saturate(dot(IN.normal, lightDir));	
	projectTexCoord.x = (IN.ViewPosition.x / IN.ViewPosition.w) /2.0f + 0.5f; 
	projectTexCoord.y = (-IN.ViewPosition.y / IN.ViewPosition.w) /2.0f + 0.5f; 	
	if((saturate(projectTexCoord.x)==projectTexCoord.x)&&(saturate(projectTexCoord.y)==projectTexCoord.y))
	{
		depthValue = tex2D(ShadowMap, projectTexCoord).r;		
		lightDepthValue = IN.ViewPosition.z / IN.ViewPosition.w;		
		lightDepthValue = lightDepthValue - bias;		
		if(lightDepthValue < depthValue)
		{
			if(lightIntensity > 0.0f)
			{
				color = (float4(1, 1, 1,1));// * lightIntensity);
				color = saturate(color);
			}
		}
	}	
	return color;
} 

// RTT Output = ShadowOverlay

Hi Phil,

When I apply a shader to an object I know exactly which textures are to be used and only the vertices's for that object are acted on. But during a post process shader, every object vertex in the scene is processed. I don't have to include every texture sampler for those objects do i?

So lets say I have a simple scene with 4 trees and each tree uses a different RGBA texture. How do I access each of those textures during the shadowmap creation step? Thats all I'm looking to get answered really.

Cheers

6

Edit. Ok, after a bit more reading it sounds like I can access the texture through something like this:

sampler2D input : register(s0);