Utilizing Vertex Layouts

[MrGuy]

Hey there, guys,
i tumbled across a little problem i got with the engine: The lack of customizable Vertex layouts.
I googled quite a while and of course searched the tuts etc. but i could not help it: There's no real information about this topic but the info that its not supported.

So: Did i miss a hint? I really need custom vertex formats for my project or i have to utilize pretty ugly (and HELLA expensive methods) for my project.
For those interested: The general topic is multiple Materials blended over a MarchingCube generated IsoSurface.


If it really is not implemented/accessible: Is there any way to change that? I guess that would involve recompiling the irrlicht engine after some changes made to the source. Any hint where to start? I dont really dug deap into all that stuff - i takle things head on and start thinking when i bump into problems.

If i missed any important information i will add them asap! Sorry in that case.


Warm regards and thanks in advance,
MrGuy

[Mel]

there is a version of Irrlicht which has support for flexible vertex formats in the SVN, maybe you want to check it

http://irrlicht.svn.sourceforge.net/vie ... -pipeline/

That is an SVN version, so it is likely to have unsolved bugs.

[MrGuy]

Thanks a lot, mel,
i downloaded, compiled it and stuff. Then i build the docu and am reading into atm.

As it seems MeshBuffers need a VertexLayout as a VertexDescriptor now which i have to implement and pass to it as an argument for the constructor? And of course i got to define the layout in the shader i guess?

If you got any tipps that might help me getting into the topic faster than crawling through sourcecode and descriptions of methods i appreciate it, otherwise i gotta stick with it.




Warm regards,
MrGuy

[Nadro]

Hi,

This is a short info about usage FVF in Irrlicht (shader-pipeline branch):
You have to register new vertex layout via "IVideoDriver::addVertexDescriptor" eg. called "MyVertexFormat", at next You have to add an attributes to "MyVertexFormat" descriptor via "IVertexDescriptor::addAttribute" eg. position, normal, texcoord and others. When You will have defined vertex descriptor You must apply it to a vertex buffer (this is part of mesh buffer) via "IVertexBuffer::setVertexDescriptor". Thats all. You'll get an acces to Your vertex values via "attribute" operator in GLSL and semantic in HLSL.

Cheers,

[Mel]

And later, if, for instance you load a skinned mesh, how can you apply that vertex layout to the loaded mesh?

[MrGuy]

Most likely load it into a standard layout first and copy it into the extended afterwards...

Since i use runtime generated meshes this shouldnt become that much of a problem.

[Nadro]

And later, if, for instance you load a skinned mesh, how can you apply that vertex layout to the loaded mesh?

You have to change a VertexDescriptor (IVertexBuffer::setVertexDescriptor) and convert vertices (IMeshManipulator::convertVertices) to properly format. I think that a good idea will be a param (bool convertVertices = true) in setVertexDescriptor which will be automatically call a convertVertices method when it is set to "true". Now Your skinned mesh will be have other vertex format.

[Mel]

Thanks for the explanation, I hope this makes it soon to the trunk of the engine

[MrGuy]

I played around with it a bit and it seems to be not as intuitive as i thought.

I tumbled across the GLSL specifications tho and found, that GLSLs standard vertex layout expects 8 UV coords. I could encode my needed information in that one if - and here comes the part i dislike here - irrlicht would offer a vertex which supported those 8 uvs.

So is there by chance a way to implement that? I looked inside the code but its utterly unclear to me how those S3DVertex' and its children are working. I would like guesses, since i find that solution better than the utilizing of vertex layouts which arent in the core release by now.


Regards,
MrGuy

[Nadro]

You can use "attribute" in GLSL instead of fixed pipeline solution - UV slots. How to use it I posted in this thread. Of course it's related just for shader-pipeline branch. A current stable release supports only S3DVertex, S3DVertex2Coords and S3DVertexTangents and we will not extend this interface, because in future releases it will be replaced by a system from shader-pipeline.

[MrGuy]

Well then. I went through all the pain of learning how to work with it ( It was quite easy, when i look back... Stupid me did some mistakes at the beginning. )

Now its working! Here we go: Marchingcubes generated isosurfaces with smooth blending between given materials ( Every blending possible )
http://imageshack.us/photo/my-images/202/matblend.png/ For those interested.

[Nadro]

Nice I am glad that FVF was useful for You in this case.

[Mel]

Let's see how long it takes for it to be included in the engine

[MrGuy]

Vertex layouts have some neat use cases.
I'm working on a vertexcollapse algorithm for now, but i will post a screenshot of my a bit more advanced Terrains. The sphere is abit boring.

Could take some time tho. I dont know how fast i will finish the VC-algorithm. I hate to operate on those nasty buffers.



Thanks a lot for your help guys.

[hendu]

Can't see the pic by clicking the link, and the direct (embed) link gives a 404...
http://img202.imageshack.us/img202/9311/matblend.png