Hi All

I have been following a few different tutorials on volume rendering using ray casting but i have come across a few issues which im hoping someone will be able to give me advice on

1. So I first render a cube front and back and then save these to textures which I use for the actual volume rendering after..... when I move the camera into the volume cube I notice the render of the front side no longer draws and only the back side draws, which this means I no longer can draw the actual volume render

[attachment=31493:display1.png]
What could I do to get around this problem as I really want to be able to move freely through the volume renders

[attachment=31494:display2.png]
2. this theory is based on the bounding volume being a area that goes from 0,0,0 to 1,1,1 and this works fine ....but if I want the volume area to only be scaled to 0.5,0.5,0.5 this now ruins the volume and its very confusing to why this would happen? I will try provide as much code for the area as possible but any advice would be great

[attachment=31495:progress.png]

Pixel Shader code for the volume render

float2 texC = input.pos.xy /= input.pos.w;
	texC.x = 0.5f*texC.x +0.5f;
	texC.y = 0.5f*texC.y +0.5f;


	float3 frontTex = txDiffuse2.Sample(samLinear, texC).xyz;
	float3 backTex =  txDiffuse.Sample(samLinear, texC).xyz;

	float3 direction = normalize(backTex - frontTex);// input.PosW);
	
	float4 pos = float4(frontTex, 0.0);
	float4 dst = float4(0, 0, 0, 0);
	float4 src = 0;

	float value = 0;

	float3 Step = normalize(direction) * 0.01;

	for (int i = 1; i < 50; i ++)
	{
		pos.w = 0.0;
		value = volume.Sample(samLinear, pos).r;
		src = (float4)value;
		src.a *= 0.5f;

		dst.rgb = dst.rgb + (1 - dst.a) * src.a * src.rgb;
		dst.a = dst.a + (1 - dst.a) * src.a;
		//src.rgb *= src.a;
		//dst = (1.0f - dst.a) * src + dst;
		if (dst.a >= .95f)
			break;

		////advance the current position
		pos.xyz += Step;

		////break if the position is greater than <1, 1, 1>
		if (pos.x > 1.0f ||  pos.y > 1.0f || pos.z > 1.0f)
			break;
	}

Vertex code for rendering the two textures

VS_OUTPUT VS(VS_INPUT input)
{
    VS_OUTPUT output = (VS_OUTPUT)0;

	input.PosL = input.PosL *float4(1, 1, 1, 1);
	float4 posW = mul(input.PosL, LocalWorld);
	//output.PosH = posW;
	output.PosW = posW.xyz;
	posW = mul(input.PosL, World);
	output.PosH = mul(posW, View);
	output.PosH = mul(output.PosH, Projection);
	output.Tex = input.Tex;

	float3 normalW = mul(float4(input.NormL, 0.0f), LocalWorld).xyz;
	output.NormW = normalize(normalW);

    return output;
}

Id be happy to help anyone who also is trying this but I fear I have either done something wrong or I am missing something

Thank You

http://www.gamedev.net/topic/656419-volume-texture-for-clouds/ This thread might help

Thanks guys I have been looking through replies ...

Kyrpt0n - when you say to render the back faces, do you mean still render them to a texture and then draw the actual cube and pass that texture through to do the ray trace with?

Hi all,

So I have come across a new problem, when the cube is rendered at 0,0,0 with a scale 1,1,1 and it seems to work well, but now i move the cube left and right hoping the volume would look the same but move and this happens

Can anyone help me understand why this now happens please?

I get that the vertex shader takes in position of the object and then this is used within the pixel shader to reference from the backtexture but I cannot see how to get the volume to move while keeping the image consistent as i am hoping to use this for particle system

Thank You