1, 在每个场景中,找到那个MainCamera,然后在Inspector上,找到MainCamera的属性,Clipping Planes,需要做的是尽量放大near的值,尽量减小far的值。根据我的实验结果,同样改动Near值的幅度比Far值的幅度相对来说效果会更好。如Near从1到20可能修正了某个z-fighting,但是Far从1000改到500也还是没有用。这个在实践中可以注意。
2, 如果场景没有办法改动上述的值,那么还有的方式就是找到产生z-fighting的模型,让模型产生这个现象的两个面尽量离开一些距离,究竟多少距离只有通过实验才知道。
3, 如果可能,程序上就可以用Polygon Offset,这个是OpenGL的接口,
drawOnePlane(); //Draw other plane in the almost same position, before use offset, it will fighting with the one we has drawn. glEnable( GL_POLYGON_OFFSET_FILL ); glPolygonOffset( g_OffsetFactor, g_OffsetUnit ); drawOtherPlane(); glPolygonOffset( 0.0f, 0.0f ); glDisable( GL_POLYGON_OFFSET_FILL );
4、如果是D3D,那么这篇文章提到3中方式,最后一种方式是跟上面的OpenGL思路一样的。
http://software.intel.com/zh-cn/articles/alternatives-to-using-z-bias-to-fix-z-fighting-issues/
a, project matrix
// ZFighting Solution #1 - Projection Matrix D3DXMATRIX mProjectionMat; // Holds default projection matrix D3DXMATRIX mZBiasedProjectionMat; // Holds ZBiased projection matrix // Globals used for Projection matrix float g_fBaseNearClip = 1.0f; float g_fBaseFarClip = 100.0f; // Code indicates no change. ie states 'near and far clipping planes pushed out' but only far appears pushed float g_fNearClipBias = 0.0f; float g_fFarClipBias = 0.5f; // Projection Matrix work around // Best if calculation are done outside of render function. // The "zbiased" projection has it near and far clipping // planes pushed out... D3DXMatrixPerspectiveFovLH( &mZBiasedProjectionMat, D3DX_PI/4,(mProjectionMat._22/mProjectionMat._11), g_fBaseNearClip + g_fNearClipBias, g_fBaseFarClip + g_fFarClipBias ); . . . // Original projection is loaded m_pd3dDevice ->SetTransform( D3DTS_PROJECTION, & mProjectionMat); // Billboards are rendered... // The "zbiased" projection is loaded ... m_pd3dDevice->SetTransform(D3DTS_PROJECTION, &mZBiasedProjectionMat); // Posters are rendered... // Original projection is reloaded... g_pd3dDevice->SetTransform( D3DTS_PROJECTION, & mProjectionMat); . . .
b, view port matrix
// ZFighting Solution #2 - Viewport D3DVIEWPORT9 mViewport; // Holds viewport data D3DVIEWPORT9 mNewViewport; // Holds new viewport data // Global used for Viewport // Hard coded for ZBIAS of 1 using this formula // MinZ - 256/(2^24-1) and // MaxZ - 256/(2^24-1) // 2^24 comes from the amount of Zbits and the 256 works // for Intel (R) Integrated Graphics, but can be any // multiple of 16. float g_fViewportBias = 0.0000152588f; // Projection Matrix work around // Viewport work around m_pd3dDevice->GetViewport(&mViewport); // Copy old Viewport to new mNewViewport = mViewport; // Change by the bias mNewViewport.MinZ -= g_fViewportBias; mNewViewport.MaxZ -= g_fViewportBias; . . . // Original viewport is reloaded … m_pd3dDevice->SetViewport(&mViewport); // Billboards are rendered … // The new viewport is loaded … m_pd3dDevice->SetViewport(&mNewViewport); // Posters are rendered … // Original viewport is reloaded … m_pd3dDevice->SetViewport(&mViewport); . . .
c, depth - bias
BOOL m_bDepthBiasCap; // TRUE, if device has DepthBias Caps // Globals used for Depth Bias float g_fSlopeScaleDepthBias = 1.0f; float g_fDepthBias = -0.0005f; float g_fDefaultDepthBias = 0.0f; // Check for devices which support the new depth bias caps if ((pCaps->RasterCaps & D3DPRASTERCAPS_SLOPESCALEDEPTHBIAS) && (pCaps->RasterCaps & D3DPRASTERCAPS_DEPTHBIAS)) { m_bDepthBiasCap = true; // TRUE, if DepthBias Caps } // Billboards are rendered... // DepthBias work around if ( m_bDepthBiasCap ) // TRUE, if DepthBias supported { // Used to determine how much bias can be applied // to co-planar primitives to reduce z fighting // bias = (max * D3DRS_SLOPESCALEDEPTHBIAS) + D3DRS_DEPTHBIAS, // where max is the maximum depth slope of the triangle being rendered. m_pd3dDevice->SetRenderState(D3DRS_SLOPESCALEDEPTHBIAS, F2DW(g_fSlopeScaleDepthBias)); m_pd3dDevice->SetRenderState(D3DRS_DEPTHBIAS, F2DW(g_fDepthBias)); } // Posters are rendered... if ( m_bDepthBiasCap ) // TRUE, if DepthBias supported { // DepthBias work around // set it back to zero (default) m_pd3dDevice->SetRenderState(D3DRS_SLOPESCALEDEPTHBIAS, F2DW(g_fDefaultDepthBias)); m_pd3dDevice->SetRenderState(D3DRS_DEPTHBIAS, F2DW(g_fDefaultDepthBias)); } . . .
5,这里还有一篇文章教到怎么样在面上画出线的,相信你也会遇到同样的问题。当然,核心还是用depth-bias,但是,人家把怎么做和做的时候要注意的问题都写上了(主要就是用bias的时候值不要取的太大,否则线框是渲染出来了,但是也同时多出线来了,因为本来是该本剪切的,经过修正可能就不被剪切了)。值得一看。
http://www.catalinzima.com/samples/12-months-12-samples-2008/drawing-wireframes-without-z-fighting/
z-fighting的出现是的不同面上的像素在z-buffer中的值相近,导致前台取像素的时候一会去这个面的,一会取那个面的。改变照相机的near、far属性会涉及到z-buffer中的值的精度。因为在各个平台上z-buffer位数不同,因此改变near和far能给z-buffer中的值的浮点数部分尽量留出空间,消除z-fighting。
这个是wiki上的z-fighting的例子,可以看到不同色彩的面,因为z-buffer的精度设置的小,然后两个面放置的比较近,因此出现了相关的穿插显示的问题。