This is a helper for drawing simple geometric shapes including texture coordinates and surface normals.
  • Cube (aka hexahedron)
  • Sphere
  • Geodesic Sphere
  • Cylinder
  • Cone
  • Torus
  • Tetrahedron
  • Octahedron
  • Dodecahedron
  • Icosahedron
  • Teapot

Initialization

The GeometryPrimitive class must be created from a factory method which takes the Direct3D 11 device context.

std::unique_ptr<GeometricPrimitive> shape(
GeometricPrimitive::CreateTeapot(deviceContext) );
For exception safety, it is recommended you make use of the C++ RAII pattern and use a std::unique_ptr.
  • CreateCube( deviceContext, float size = 1)
  • CreateSphere( deviceContext, float diameter = 1, size_t tessellation = 16)
  • CreateGeoSphere( deviceContext, float diameter = 1, size_t tessellation = 3)
  • CreateCylinder( deviceContext, float height = 1, float diameter = 1, size_t tessellation = 32)
  • CreateCone( deviceContext, float diameter = 1, float height = 1, size_t tessellation = 32)
  • CreateTorus( deviceContext, float diameter = 1, float thickness = 0.333f, size_t tessellation = 32)
  • CreateTetrahedron ( deviceContext, float size = 1)
  • CreateOctahedron ( deviceContext, float size = 1)
  • CreateDodecahedron ( deviceContext, float size = 1)
  • CreateIcosahedron ( deviceContext, float size = 1)
  • CreateTeapot( deviceContext, float size = 1, size_t tessellation = 8)

Simple drawing

Simple solid shape drawing:
shape->Draw(world, view, projection, Colors::CornflowerBlue);

Simple wireframe shape drawing:
shape->Draw(world, view, projection, Colors::Gray, nullptr, true);

Simple solid textured shape drawing:
shape->Draw(world, view, projection, Colors::Gray, cat);

The Draw method also accepts an optional callback function which can be used to override the default rendering state:
shape->Draw(world, view, projection, Colors::White, catTexture, false, [=]
{
    deviceContext->OMSetBlendState(...);
});
This makes use of a BasicEffect shared by all geometric primitives drawn on that device context.

Advanced drawing

This form of drawing makes use of a custom Effects instance. The caller is responsible for using an input layout that matches the effect.

IEffect* myeffect = ...

Microsoft::WRL::ComPtr<ID3D11InputLayout> inputLayout;
shape->CreateInputLayout( myeffect, inputLayout.GetAddressOf() );

shape->Draw( myeffect, inputLayout.Get() );

This takes an optional parameter for enabling alpha-blending, wireframe, and a callback function which can be used to override the default rendering state.

The Draw operation will only set up a texture sampler in slot 0. If you are using an effect with more than a single texture, you need to set additional samplers manually (perhaps via setCustomState callbacks). For example, if using DualTextureEffect or EnvironmentMapEffect:

shape->Draw( myeffect, inputLayout.Get(), false, false, [=]
{
    ID3D11SamplerState* samplerState[2] = { states.LinearClamp(), states.LinearWrap() };
    deviceContext->PSSetSamplers(0, 2, &samplerState);
});

Coordinate systems

These geometric primitives (based on the XNA Game Studio conventions) use right-handed coordinates. They can be used with left-handed coordinates by setting the rhcoords parameter on the factory methods to 'false' to reverse the winding ordering (the parameter defaults to 'true').

std::unique_ptr<GeometricPrimitive> shape(
GeometricPrimitive::CreateTeapot( deviceContext, 1.f, 8, false ) );

Note: Using the wrong value for rhcoords for your viewing setup will result in the objects looking 'inside out'.

Alpha blending

Alpha blending defaults to using premultiplied alpha. To make use of 'straight' alpha textures, override the blending mode via the optional callback:

CommonStates states(deviceContext);

shape->Draw(world, view, projection, Colors::White, catTexture, false, [=]
{
    deviceContext->OMSetBlendState( states.NonPremultiplied(), nullptr, 0xFFFFFFFF);
});

Feature Level Notes

In order to support all feature levels, the GeometricPrimitive implementation make use of 16-bit indices (DXGI_FORMAT_R16_UINT) which limits to a maximum of 65535 vertices.

Feature Level 9.1 is also limited to a maximum of 65535 primitives in a single draw. This rule out using extremely large numbers for the tessellation factor, although the exact limit depends on the shape implementation.

Note that these shapes tend to duplicate rather than share vertices in order to provide the 'face-normal' lighting expected of sharp geometry.

Threading model

Each GeometricPrimitive instance only supports drawing from one thread at a time, but you can simultaneously submit primitives on multiple threads if you create a separate GeometricPrimitive instance per Direct3D 11 deferred context.
http://msdn.microsoft.com/en-us/library/windows/desktop/ff476892.aspx

Remark

Tetrahedron, Cube/Hexahedron, Octahedron, Dodecahedron, and Icosahedron comprise the five "Platonic solids". The Utah Teapot is sometimes referred to as the "Sixth Platonic solid" due to its prevalence in rendering sample images.

Further Reading

http://msdn.microsoft.com/en-us/library/windows/desktop/ff476876.aspx

http://blogs.msdn.com/b/chuckw/archive/2012/06/20/direct3d-feature-levels.aspx

http://en.wikipedia.org/wiki/Cube
http://en.wikipedia.org/wiki/Hexahedron
http://en.wikipedia.org/wiki/Sphere
http://en.wikipedia.org/wiki/Cylinder_(geometry)
http://en.wikipedia.org/wiki/Cone
http://en.wikipedia.org/wiki/Torus
http://en.wikipedia.org/wiki/Tetrahedron
http://en.wikipedia.org/wiki/Octahedron
http://en.wikipedia.org/wiki/Dodecahedron
http://en.wikipedia.org/wiki/Icosahedron
http://en.wikipedia.org/wiki/Utah_teapot
https://en.wikipedia.org/wiki/Platonic_solid

Last edited Mar 14 at 6:54 PM by walbourn, version 38