# aprilspirit89

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1. ## How to orthogonalize to non-orthogonal matrix using HLSL

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. ## How to orthogonalize to non-orthogonal matrix using HLSL

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. ## Could Parallax Mapping be done at World Space?

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. ## UV mirror issues with normalmap , using nonprecomputed tangent space calculating

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. ## UV mirror issues with normalmap , using nonprecomputed tangent space calculating

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. ## How to switch Perspective to Orthogonal projection while keeping things in almost same size?

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. ## How to modify the surface data using LockRect

My mistake.More time spend when modifing data,so the render data for next frame wasn't updated properly, which bothered me 2 days.

9. ## How to modify the surface data using LockRect

I'm trying to save render sth. to texture and modify the data before saving it to file.But I found the data incorrect when I modify them. [source lang="cpp"] LPDIRECT3DSURFACE9 pBackBuffer,pRenderSurface=NULL; g_pd3dDevice->CreateRenderTarget(width,height,D3DFMT_A8R8G8B8,D3DMULTISAMPLE_NONE,0,TRUE,&pRenderSurface,NULL); hResult = g_pd3dDevice->GetRenderTarget(0,&pBackBuffer); g_pd3dDevice->SetRenderTarget(0,pRenderSurface); g_pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DXCOLOR(0,0,0,0), 1.f, 0); Render(); g_pd3dDevice->SetRenderTarget(0,pBackBuffer); D3DLOCKED_RECT rect; if(S_OK == pRenderSurface->LockRect(&rect,NULL,D3DLOCK_NOSYSLOCK)) { DWORD* pColor = (DWORD*)rect.pBits; for( UINT y = 0 ; y < height ; y++ ) { for(UINT x = 0 ; x < width ; x++ ) { DWORD color = pColor[y*rect.Pitch/4+x]; D3DCOLOR dwcolor = color; D3DXCOLOR fColor = Color2Value(dwcolor); if(fColor.a > 0) { fColor.r /= fColor.a; fColor.g /= fColor.a; fColor.b /= fColor.a; } dwcolor = Value2Color(fColor); pColor[y*rect.Pitch/4+x] = dwcolor; } } pRenderSurface->UnlockRect(); } D3DXSaveSurfaceToFile(pTexPathName,texFormat,pRenderSurface,NULL,NULL);[/source] Here is the code.I tried every D3DLOCK flags but none of them work. I also try CreateOffscreenPlainSurface and GetRenderTargetData to copy the surface data to system memory before LockRect.Also Failed.Did I miss Something?
10. ## Location of D3DTS_WORLD value in register

Thanks! I'll change my code anyway.
11. ## Location of D3DTS_WORLD value in register

I wonder if I can get world matrix in shader using register.I wrote this in C++ and used a fixed pipeline: [source lang="cpp"]g_pd3dDevice->SetTransform(D3DTS_WORLD, &matWorldSave);[/source] Now I want to add a shader,and use world matrix without changing code above.For example,I can use register s0 to represent the first texture in shader.Which register should I use?
12. ## Particle Blend Issue with premultiplied alpha

You're very helpful.I thought doing multiply alpha it in shader is equal to doing it in making assert stage.Yes,my problem maybe not the proper customer for pre-multiplied alpha technique.But so far,it's the closet way,because I have good result about alpha blend mode(srcAlpha VS 1-srcAlpha). As said above,I am rendering 3D particle sytems in 3D world,then I'm trying to save them to 2D texture arrays,so that they can be reused to 3D or 2D game world.I got a texture seems alright but shows black edges in Photoshop.They are inflenced by the default back ground color.I described my problem here. What the PS accept is straight alpha,which is opposite to pre-multiplied alpha.RGB value should be independent from alpha.But rgb is definitely influnced by alpha during rendering process.So I tried to get rid of it.Because I got both premultilied alpha texture(particle resource) and unpremultiplied ones,I use mix alpha mode,additive and blend.Just devide rgb by alpha won't work.I studied premultiplied alpha and it gives me an inspiration,so I separate alpha calculation.It works well with alpha blend mode,while additive mode still remains unsolved.
13. ## Particle Blend Issue with premultiplied alpha

Thank you very much.Now I'm a little confused.You said I can keep alpha value to 0,to vary the strength of additive mode.But I can't see other way except to change the source alpha.I do the premultiplication in PS shader,then set alpha to 0.And the pipeline will do the alpha blend thing like this OutColor=Src.rgb+Dest.rgb*(1-0) OutColor=Src.rgb+Dest.rgb //srcColor 1 //destColor 1-srcAlpha Then I get correct color and wrong alpha.Did I do it in a wrong way?
14. ## Particle Blend Issue with premultiplied alpha

Thank you for your reply.I had tried the original pre-multiplied alpha technique.But I must set alpha to 0 when I use additive mode,that destroy the final alpha.
15. ## Particle Blend Issue with premultiplied alpha

I was trying to save some texture from 3D rendering scene,and then get them to reuse. The big problem is that rgb value can not match its alpha value.I need some picture without black edge,so I must use rgb colors to divide its alpha value(Image manipulation software such as Photoshop can just deal with picture which alpha channel is nonpremultiplied.) Unfortunally,the color is too light that some result value are cut off to 1. So I turned to a technique called premultiplied alpha.(See more). Instead of using shaders,I just use separate alpha calculation. For example: RenderState.SourceBlend = Blend.SourceAlpha; RenderState.DestinationBlend = Blend.InverseSourceAlpha; Now I add some renderstate. RenderState.SourceBlendAlpha = Blend.One; RenderState.DestinationBlendAlpha = Blend.InverseSourceAlpha; It works well.But when I try to handle following things: RenderState.SourceBlend = Blend.SourceAlpha; RenderState.DestinationBlend = Blend.One; RenderState.SourceBlendAlpha = Blend.One; RenderState.DestinationBlendAlpha = Blend.One; The result is totally wrong. Because when I use nonpremultiplied blend state,which is SourceAlpha and inverseSourceAlpha.The rgba value is definitely controlled within 0~1.But when I switch to additive state,which is SourceAlpha and 1,the rgb values might be over one,thus cause the incorrect value. Now my problem is how to control the alpha value,to make sure it keep all details and do not overflow at the same time? //Modified PS:If you don't understand what I am trying to do,there is a commercial software called "Particle Illusion".You can create various particles and then save the scene to texture,where you can choose to remove background of particles. [attachment=9970:particleIllusionDemostrate.png]