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Post-process shader chaining

A (single) post process effect is achieved by firstly rendering the scene to a framebuffer with appropriate attachments outputting the result to a texture, applying the texture to a full screen quad, specifying an output framebuffer (usually the default framebuffer) and then executing a shader on the texture to render to the output framebuffer (the screen). To chain you take the output framebuffer and feed it as input to another post process effect using the same sequence as before. The final shader (the final link in the chain) is then output to the screen (i.e. the main framebuffer). For performance reasons of course it’s better to have an uber-shader but the support’s there. I’ve made it so adding post processing shaders to the engine / editor is painless (you simply drop them into a special folder that the editor scans on start-up – which then generates a factory / menu item entry for each effect – the same approach I take for regular non-post-process shaders in the engine / editor). Here’s a video of a vignette -> pixelate -> chromatic aberration post processing chain in action in the editor:

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Unit Testing across Linux, macOS and Windows

As SimulationStarterKit is C++ / CMake based I use CTest as the unit testing framework that’s especially helpful when you’re trying to cover a few platforms (i.e. Linux, macOS and Windows). Every time I implement a feature in the engine I try to create a corresponding test first to help determine what constitutes correct operation and also sometimes as a programming aid to help discover what a usable API might look like for a new feature. The video below demonstrates how this looks in Visual Studio.

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Pixel perfect object movement

A standard feature of all 3D scene editors are object transform manipulation tools, i.e. translate, rotate and scale. Whilst there are articles that describe the behavior I couldn’t find a specific article on the implementation details so thought I’d write up the algorithm I use. Continue reading Pixel perfect object movement

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Cross compiling C/C++ libraries for Android (updated)

There are a few forms a C/C++ library that you want to cross compile to Android might come in.

For instance:

  • An Autotools project
  • A CMake project

To get started let’s make a standalone Android toolchain (a toolchain being compilers, libraries and headers for cross compiling our source code to a specific target architecture and platform ABI) . Continue reading Cross compiling C/C++ libraries for Android (updated)

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Occlusion culling

Occlusion culling complements frustum culling by culling occluded objects. Frustum culling is an optimisation technique that discards meshes that sit outside of the viewing volume by testing each mesh against the six frustum planes. The culling can be accelerated with hierarchical spatial partitioning whereby the scene is carved up into a tree with each tree node representing a smaller region of space. A node contains all render-able objects enclosed in the node’s space allowing fast inclusion / rejection of the node objects. If, a node is found to intersect the viewing volume then the algorithm recurses down into the node’s child nodes etc.

That’s great however more can still be done. Continue reading Occlusion culling

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Post-processing shaders

Added post-processing shader support to the engine. Post-processing shaders can be used to apply full screen effects to scenes. Examples of such shaders include full-screen anti-aliasing, vignette effects and motion blur to name but a few. With a post processing shader the scene is typically rendered to a texture that is bound to an off screen frame buffer with appropriate depth and color attachments. The texture is then applied to a full screen quad and rendered to screen. This short clip demonstrates the post processing shader.