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dragon.R

Member Since 02 Apr 2011
Offline Last Active Oct 21 2013 02:59 AM

Topics I've Started

Environment Map for large scale outdoor scene

14 September 2013 - 07:44 AM

Hi~I've read some papers about using an environment cube map for secondary specular lighting and want to try this in my engine, but I don't know very clearly about how to create environment map for an outdoor scene, since the scene is so large, and different area may need different cube maps. If I create them on several places, how can I make sure all the objects can sample the right light infomation, especially for the dynamic objects? If I create cube maps for every single object,then the memory cost may be a problem,and this also cause problems when I deal with the moving object.So how do current game engine usually manage their environment maps? 


How to deal with mipmaps on the mirrored mesh?

03 September 2013 - 10:56 PM

Hi~Recently I downloaded some skined meshes for my demo,some of them were mirrored and just have a half of contents in the texture(since the UV in mesh were also mirrored). Then I found a problem that when the mip level increases,a black line appears in the middle of mesh.Is it because the GPU  samples some background color in the border of the actual image content when  I sample the smaller mipmap? How can I sovle this problem ? Do I need to make some bias or clamp the mip level ?


The precision problem of matrix transformation

11 April 2013 - 09:35 PM

Yesterday I found a problem of my demo, when the object and camera were far away from (0,0,0), such as  an object at (2000,2000,0) and camera at (2010,2000,0) , the accuracy of Z seemed to declined, lots of Z-Fighting problems appears.

 

The transform code of my model is:

 

output.oPosition=mul(output.oPosition,WorldMatrix);

output.oPosition=mul(output.oPosition,ViewProj);

 

When I change to :

 

output.oPosition=mul(output.oPosition,WorldViewProj);

 

It became just ok.

 

Sometimes I need to transform the object to the world space first and do some other transformations, so I'm afraid this problem will apear again,and I don't know why this two pieces of code have such a big difference.


FPS rise suddenly every few seconds

26 February 2013 - 02:55 AM

Hi. My demo runs well on my HD5670 home computer,but I don't know why when I test it on GT430,the FPS becomes not steady.In most of time it runs at about 30+ frames per second,but every few seconds it well suddenly rise to 200+ frames per second and drop to 30+ immediatly on the next frame. This problem causes my demo runs not smoothly on that machine, and when I lock the frame rate to 30,it became just ok. Does anyone know the reason?


Deferred decal and texel offset

12 November 2012 - 12:44 AM

I have implemented the deferred decal this weekend, I'm using Direct3D9 and hacked the depth buffer as a rendertexture(FOURCC('I','N','T','Z')).Every decal is a cube box.To find the uv coordinate of decal pixels,I have to sample the depth texture and caculate the world position of each pixel,then transform the position to decal space. My problem is, when I have an object in front of the decal,there will be some bright edges around the object.It seems that the depth result on the edge is not currect. I've tried to add 0.5 pixel offset, but it not works.Can someone help me?

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