This is an effort to implement Hello Triangle using the Mantle API by using the API reference and reverse engineering public Mantle demos.
See this blog post for more information:
https://medium.com/@Overv/implementing-hello-triangle-in-mantle-4302450fbcd2
The reference
is used as primary resource, because it contains a full API reference and some
sample code. Unfortunately it misses a lot of the constant definitions, like
GR_API_VERSION, but these can be determined by creating a proxy mantle64.dll
that logs calls and the contents of structs. This approach is currently used
on the Star Swarm Stress Test to
figure out what calls and data are needed to render a triangle on the screen.
Other values, like GR_MAX_HEAPS can be figured out by querying for the struct
size with functions like grGetObjectInfo.
The intermediate language used for Mantle shaders is a subset of AMD IL, for which CodeXL contains a compiler. The disassembly it outputs is incorrect, but the bytecode itself is valid. Mantle appears to accept this code without problems.
The code is capable of creating a window using the SDL library, clearing it to black and rendering a per-vertex colored triangle using Mantle.
The vertex shader reads the position (float4) and color (float4) from a
buffer using the SV_VertexID built-in variable. Each buffer is assigned a
memory view into GPU memory filled with the following data:
float vertices[] = {
// Positions
0.0, 0.5, 0.0, 1.0,
0.5, -0.5, 0.0, 1.0,
-0.5, -0.5, 0.0, 1.0,
// Colors
1.0, 0.0, 0.0, 1.0,
0.0, 1.0, 0.0, 1.0,
0.0, 0.0, 1.0, 1.0
};
Shaders are written in HLSL and compiled to AMD Intermediate Language using
the CodeXLAnalyzer.exe tool included in CodeXL using the --il flag. A batch
script for doing this is included in the shaders folder. The hex code on the
right side can then be converted to a binary file using the output2binary.py
script, which takes the IL output file name as parameter. The binaries can then
be loaded into Mantle using grCreateShader, as is demonstrated in the code.
Copyright (c) 2015 Alexander Overvoorde
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