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Daniel Wilson

Member Since 31 May 2012
Offline Last Active Aug 26 2012 04:16 PM
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Topics I've Started

How to change colour based on viewing angle

13 August 2012 - 02:52 PM

I would like to fake some caustics on a glassy surface very quickly, and the idea I have is to overlay a static caustic texture that appears based on the viewing angle, so when the angle is more grazing, more of the texture appears. How might I do this? A small piece of code would be seriously amazing.

Thankyou!

When to normalize vectors in a shader?

02 August 2012 - 06:43 AM

Hi, I am currently working on a shader and the result is not quite right. One question that bugs me I cannot seem to find the answer to is why and when exactly we normalize vectors in a shader. I understand that it seems to only be important for direction vectors such as the light, but is it important to do so in certain spaces with other vectors aswell? I took a naive approach at first and normalized all the time. I am not so much concerned with efficiency, just why and when it is okay or not okay to normalize a vector.

For example, the shader I am writing at them moment requires the vector from the view position to the vertex position in world space. Some shaders I see normalize this when it is in the fragment shader, but does that not destroy the value of the vector for further calculations?

Tool to mathematically create a mesh

17 July 2012 - 07:59 AM

Hi I need a good tool to mathematically create a surface and then get it into 3ds max, for example a sphere is defined algeraically as x^2 + y^2 + z^2 = r^2. Any examples? The only one I can find is 3D-Math Xplor, but the full version only works on a mac and I have Windows 7. The Java version that works on all platforms does not have the export functionality!

What to do with an attenuated light vector in my shader

05 July 2012 - 11:22 AM

Hi, I am working on implementing a subsurface scattering light shader and have it all coded I just need to debug. I have a question I cannot solve though, say I have the attenuated light vector that has come from the light, scattered as it enters the surface of the object, and now goes to the viewers eye. What would I do with this output vector for for a mesh that has a standard Blinn-Phong shader? The image has the vector I am talking about, vector PC



Posted Image

In my normal lighting shader I have this:


float3 l = normalize(IN.light.xyz - IN.oPosition);
   float3 v = normalize(IN.oPosition);
  
   // compute diffuse and specular terms
   float diff = saturate(dot(l,IN.normal));
   float spec = saturate(dot(normalize(l-v),IN.normal));
   spec = pow(spec, shine);
   // attenuation factor
   float att = saturate(dot(l, IN.normal));
	
   // compute final color
   float3 finalcolor;
   finalcolor =  ambient.xyz*color.xyz +
	 att*(color.xyz*diffuse.xyz*diff +
	 specular*spec);

   return float4(finalcolor.xyz, 1.0);

With no normal map or anything, how might I slot PC into this code. I'm thinking it would replace the view direction v that I have. Someone else told me the *= it with the final colour, but that just produces weird rainbow type colours, and my light is white

Floating point texture in FX Composer

02 July 2012 - 09:36 AM

Hi, I need to use FX Composer because I have to debug my shader. I was using Ogre and cg (ps_3_0) before. Previously my app saved values to a floating point texture (containing a matrix) which was passed to the cg shader file. Does anyone know if it's even possible to create a matrix in fx composer, and save it to a floating point texture for future lookups? All I see in FX Composer is the ability to create color and depth targets.

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