Difference between revisions of "Horde3D Wiki:HOWTO"

Revision as of 20:51, 27 August 2009

The HOWTO contains quick answers for smaller problems.

How to enable anti-aliasing (MSAA)

Anti-aliasing can only be enabled for render targets. The RenderTarget element used in Pipeline resources has an attribute maxSamples which defines the maximum number of samples used for MSAA. The actual number of samples is controlled by the engine option SampleCount. This makes it possible to control the anti-aliasing quality from the application. If SampleCount is set to zero, MSAA is disabled. Note that the hardware needs to support the EXT_framebuffer_multisample extension in order for the MSAA to work.

How to get the size of a loaded texture

The following code queries the dimensions of the base mipmap of a loaded texture:

int width = h3dGetResParamI( texResHandle, H3DTexRes::ImageElem, 0, H3DTexRes::ImgWidthI );
int height = h3dGetResParamI( texResHandle, H3DTexRes::ImageElem, 0, H3DTexRes::ImgHeightI );

If you want to get the dimensions of mipmap level n, change the elemIdx parameter which is 0 above to n.

How to modify vertex data

Vertex data is stored as streams in geometry resources. A pointer to the vertex data can be obtained by mapping a stream. The following code modifies the y coordinates of all vertex positions stored in the specified geometry resource.

int vertCount = h3dGetResParamI( myGeoRes, H3DGeoRes::GeometryElem, 0, H3DGeoRes::GeoVertexCountI );
float *pVertPosData = (float *)h3dMapResStream( myGeoRes, H3DGeoRes::GeometryElem, 0, H3DGeoRes::GeoVertPosStream, true, true );

for( int i = 0; i < vertCount; ++i )
{
    pVertPosData[i * 3 + 1] = pVertPosData[i * 3 + 1] * 2;
}

h3dUnmapResStream( myGeoRes );

How to exchange a texture of a mesh

Consider you want to exchange the diffuse texture (sampler named albedoMap) of a given mesh (with node handle myMesh) by a texture resource with resource handle myNewTex. You can do that with the following code:

H3DRes matRes = h3dGetNodeParamI( myMesh, H3DMesh::MatResI );
int idx = h3dFindResElem( matRes, H3DMatRes::SamplerElem, H3DMatRes::SampNameStr, "albedoMap" );
h3dSetResParamI( matRes, H3DMatRes::SamplerElem, elemIdx, SampTexResI, myNewTex );

First you need to retrieve the material used by the mesh. After that, you can find the desired sampler in the material. Finally, once you have the sampler index, you can access the sampler data and override its texture resource.

Note: The code above changes directly the material resource. If several meshes are using the same material, all of them will have the new texture. If that is not desired, you can create a private copy of the material by cloning it.