Rendering Order

Front to back or back to front...
Ever since the first game I wrote I always drew the background first with depth test disabled and then the characters and buildings with depth test enabled ... This is exactly how we render a scene in Adrian. But we could be rendering the foregrounds first so the number of pixels touched is minimal. This has to be done with depth test enabled of course...

Fixed Pipeline Rendering

The scene composer i had in place for the rendering engine seemed to be working fine but yesterday bhanu complained that there wasnt' a way to disable the shaders and render using just the fixed pipeline. He quickly put up a flag that disables the multipass rendering in the scene composer. But unfortunately that didn't work out as expected .. and guess who is to blame.. :D yes your truely "VK" i messed up the scene->reset() part which requires that the lists of objects for each pass be cleared for each rendering (since its' just list of pointers it doesn't really take that long to work out). Any way if we have a post processing phase (in the multipass) we have a fullscreen polygon in the final pass. There was no way of adding this for everypass so i just added it once in the constructor and in the reset i was avoiding clearing the last pass and guess what happens when there is only one pass and you call reset on the scene composer? :) and thats' what happened exactly.. so i fixed that code and now the scene composer adds a full screen poly for the post processing during multi pass rendering. I should probably add a post proc enable flag to make sure i can enable/disable this but i guess that can wait. For now the fixed pipe line is fixed and is made default :) if you want the fancy glsl shaders you should be using "--enable-shaders" (without quotes) as command line argument to start with these shaders.

PS: sorry no pictures :D

Adrian Got Shadow Mapping

I've finally finished adding another feather in the HD league. Shadows are a good way of showing the object positions etc in the world. I've finally added the ShadowMapping pass to our codebase and have actually cleaned up the code a little to treat the Shaders as objects rather than just the GLuint handles. Any way It's far from perfect, the aliasing effect is pretty evident.. the depth map is pretty high res (equal to the size of the rendering buffer) but the artifacts are there because of the huge frustum size that i had to specify for the light so as to fit the whole map.

Any way It's a good start. Ill' be looking out for ways to fix this but for now I think this is a good feature to have. Finally one of the games i created.. has shadows :D

It took me a while to get the thing working.. i was stuck with various silly problems.. but im' glad i got it done. For some tech details.. here is the sequence that i use to get the shadow rendering done. (Note .. the shadow map is rendered before every frame even for the static objects (map) but that's the only solution when we don't have a proper terrain etc to do shadow mapping offline and use that.)

• Create FrameBuffer with DepthBuffer only
• Enable and Set PolygonOffset(1.0, 1.0) // generally used value.
• Render The scene you want to get a shadow of (map + hero) from lights perspective
  
• Store the light matrix.(Light_MVP)
• Disable PolygonOffset
  
• Use Vertex and Fragment shaders for setting the color based on shadow map. (depth buffer sent as texture and is the ShadowMap)
• Send the Light_MVP to shader using mat4 uniform variable. (not using the texture matrix hack, coz this is cleaner to me).

You can check out the code @code.google.com/p/adrian

Post Processing

If you have seen my prev post, you already know iv'e been hard at work creating something using the GLSL Shaders. Well iv'e been adding a Post-Processing pipeline to Adrian's graphics engine. And i'm really excited about the results iv'e achieved with it .. So without further ado.. here are the screenies..



I know the toon shader has been done a million times now.. but the special thing about this one is ... it is done as a post-process step instead of while rendering. I know it sux.. but if you can achieve one more effect during post processing its just icing on the cake .. isn't it? :D

GLSL MultiTexture CheckList

Most of the tutorials about glsl cover the GPU side of things and generally leave out the host (CPU) side of the code to your imagination.. well not exactly .. but they assume you get it right. Turns out.. its' not that straightforward afterall.. or atleast not for me. So Here is a check list you need to see for getting multi texturing (multiple uniform variables in Fragment shader) to work.

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, tex0id); // general texture bind call we all know and love.
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, tex1id);

glUseProgram(program); //program is the shader program you create using glCreateProgram() call.
GLint h0 = glGetUniformLocation(program, "tex0");
GLint h1 = glGetUnifromLocation(program, "tex1");
glUnifrom1i(h0, 0); //first texture sampler
glUniform1i(h1, 1); //second texture sampler.

The code for Fragment Shader corresponding to the above cpu code is as follows

uniform sampler2D tex0;
uniform sampler2D tex1;
void main()
{
gl_FragColor = texture2D(tex0, gl_TexCoord[0].st) + texture2D(tex1, gl_TexCoord[0].st);
}

So Now the check list:

• Use glActiveTexture for each texture unit
• Use 0, 1, .. texture unit index while assigning values to uniform values.
• Call glUseProgram() before trying to set uniform values.
• Bind texture with texture id for each glActiveTexture.

I know this might look silly but iv'e seen a lot of people asking for this particular problem.. and sadly.. I struggled to get this right too... and this is a post to make sure i dont' ever have to go through that pain again...

Adrian v1.0 RELEASED!

At last I ironed out the bugs in the 1.0 branch and was able to release Adrian both for Windows and Linux. You can download the Linux version or the Pre-Compiled Windows Version.

Hope you guys enjoy the game. Do report any bugs you find here.

Source code is licensed under GPLv3 and the SVN repository is located here.

Here are some screenshots from the game (scaling them reduced the quality here)

New Model Loader

One of the sore points of the original game was that buildings attributes were handcoded. This was a very tedious effort. Also not to mention the results were not too appealing always, and the visual complexity of the objects was exceedingly little. But now by leveraging a third party Model loader, the loading of almost all formats has become a simple cake walk.

Thanks to ASSIMP, hosted at http://assimp.sourceforge.net/, we were able to load not just MD2, but even open source models like Collada etc. This has opened up a whole new array of resources for us. Also it lets us do away with the current MD2 loader which is pretty brittle. Even Skeleton animation can be included too if required.

However, Release 1.0 will be shipped without this feature.