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aprilspirit89

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About aprilspirit89

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  1. I can't.The matrix itself was generate in shader.In fact, I 'm trying to do normal mapping without precomputed tangent attribute in vertex buffer.The technique can be found in ShaderX5, Chapter2.6.It provides a non-orthogonal tangent-to-local matrix,so I'm trying to get the local-to-tangent matrix so that I can do lighting calculations in tangent space.
  2. Hi,I'm just wondering whether this can be done in ps shader.I have an non-orthogonal matrix and need to orthogonalize it and using inverse-?transpose result.I turned to matlab for help,only found their instructions a bit of complicated for shaders.It might influence the performance.So is there a solution yet?Thanks for any reply:)   PS:Image below shows the result of using origin matrix and do lighting in world space. [attachment=13379:Right.png] And this is the wrong result of orthogonalize the origin matrix and then using the inverse-transpose one and do lighting in tangent space. [attachment=13380:wrong.jpg] And here is my Orthogonalization code. float3x3 Orthogonalization_Schmidt(float3x3 OrginMatrix) { float3 a1 = OrginMatrix[0]; float3 a2 = OrginMatrix[1]; float3 a3 = OrginMatrix[2]; float3 b1 = a1; float3 b2 = a2 - dot(a2,b1)/dot(b1,b1)*b1; float3 b3 = a3 - dot(a3,b1)/dot(b1,b1)*b1 - dot(a3,b2)/dot(b2,b2)*b2; return float3x3(normalize(b1),normalize(b2),normalize(b3)); }    
  3. Hello,I am trying normal map and I calculate TBN matrix in pixel shader.Problem is the technique I use give a TBN matrix which is not a orthogonal matrix.It can only translate vectors from tangent space to local space,not the opposite way.So I just do lighting in world space. I just wonder can I do parallax mapping in world space or view space?If I can't,is there a way to calculate a orthogonal TBN matrix in ps?And what else technique must have tangent space? Thanks for reply.
  4. Thanks for replying my problem. Things are not the way I thought.The problem is not about UV seams at all,but the UV directions.The truth is I was using directx sampling texture directions to calculate my Binormal,that is having a V direction from top to down.But I haven't check my resources.They are bulit in Maya,which have a down-to-top V direction.So it's OK with color and fails correct normal mapping.Without my artist,I could never know this.
  5. Hi,I'm trying to do normalmap using directx9.After reading 2.6 Normal Mapping without Pre-Computed Tangents by Christian Schueler ,I deside to use this. [source lang="cpp"]float3x3 ComputeTangentFrame(float3 N,float3 p,float2 uv) { float3 dp1 = ddx(p); float3 dp2 = ddy(p); float2 duv1 = ddx(uv); float2 duv2 = ddy(uv); float3x3 M = float3x3(dp1,dp2,cross(dp1,dp2)); float2x3 inversetransposeM = float2x3(cross(M[1],M[2]),cross(M[2],M[0])); float3 T = mul(float2(duv1.x,duv2.x),inversetransposeM); float3 B = mul(float2(duv1.y,duv2.y),inversetransposeM); return float3x3(normalize(T),normalize(B),N); }[/source] It seems good and simple,but soon I get punished at little seams with UV mirrors.The whole model looks right under light,but at those seams,normal gets wrong and light reflect in unproper way,so a sudden change or miss lighting on surface appears.I think this is because when current pixel is shared by different triangles with different directions of UV,the ddx and ddy instruction will get wrong answers. So,I use [source lang="cpp"]float r = (dot(cross(T,B),N)<0.0f) ? -1.0f : 1.0f;[/source] to judge whether UV was mirrored.Then I realized I can't change tangent or binormal or normal,for most part of the mesh already seems right.On the other hand,I cannot know whether it's U mirror or V mirror.It's hard to tell the right direction of two axes(tangent and binormal) when you only know one axes(Normal).The author do not give futher information. Btw,because I'm using dx9,so I can't split vertexes in shader. So I want to know is there a possible way to solve this problem?Thanks for any reply
  6. Hi,I want to change my projection matrix from Persective to Orthogonal way.I use the same width,height and other properties,so I get bigger things showing on the screen.My question is how to modify the projection matrix so I can get simillar size as Perspective Projection?
  7. Focus on Game Graphics Programming
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