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Add love.graphics.drawShaderVertices (name subject to change).

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It draws a number of vertices, or a number of indices from an index buffer, without using any vertex data from a vertex buffer. A custom shader is required while using it.

It is useful when a custom GLSL3 vertex shader which uses love_VertexID is used to pull or compute per-vertex information from other sources.
This commit is contained in:
Alex Szpakowski
2022-01-03 14:33:54 -04:00
parent de89f5a9eb
commit 0c4be3d5e3
3 changed files with 109 additions and 0 deletions
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src/modules/graphics/Graphics.cpp
+69
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@@ -1516,6 +1516,75 @@ void Graphics::drawInstanced(Mesh *mesh, const Matrix4 &m, int instancecount)
mesh->drawInstanced(this, m, instancecount);
}
void Graphics::drawShaderVertices(PrimitiveType primtype, int vertexcount, int instancecount, Texture *maintexture)
{
flushBatchedDraws();
if (!capabilities.features[FEATURE_GLSL3])
throw love::Exception("drawShaderVertices is not supported on this system (GLSL3 support is required.)");
if (Shader::isDefaultActive() || !Shader::current)
throw love::Exception("drawShaderVertices can only be used with a custom shader.");
if (vertexcount < 0 || instancecount < 0)
throw love::Exception("drawShaderVertices vertex and instance count parameters must not be negative.");
Shader::current->validateDrawState(PRIMITIVE_TRIANGLES, maintexture);
VertexAttributes attributes;
BufferBindings buffers;
DrawCommand cmd(&attributes, &buffers);
cmd.primitiveType = primtype;
cmd.vertexCount = vertexcount;
cmd.instanceCount = std::max(1, instancecount);
cmd.texture = maintexture;
draw(cmd);
}
void Graphics::drawShaderVertices(Buffer *indexbuffer, int indexcount, int instancecount, int startindex, Texture *maintexture)
{
flushBatchedDraws();
if (!capabilities.features[FEATURE_GLSL3])
throw love::Exception("drawShaderVertices is not supported on this system (GLSL3 support is required.)");
if (!(indexbuffer->getUsageFlags() & BUFFERUSAGEFLAG_INDEX))
throw love::Exception("The buffer passed to drawShaderVertices must be an index buffer.");
if (startindex < 0)
throw love::Exception("drawShaderVertices startindex parameter must not be negative.");
if (indexcount < 0 || instancecount < 0)
throw love::Exception("drawShaderVertices index and instance count parameters must not be negative.");
if ((size_t)(startindex + indexcount) > indexbuffer->getArrayLength())
throw love::Exception("drawShaderVertices startindex and index count parameters do not fit in the given index buffer.");
if (Shader::isDefaultActive() || !Shader::current)
throw love::Exception("drawShaderVertices can only be used with a custom shader.");
Shader::current->validateDrawState(PRIMITIVE_TRIANGLES, maintexture);
VertexAttributes attributes;
BufferBindings buffers;
DrawIndexedCommand cmd(&attributes, &buffers, indexbuffer);
cmd.primitiveType = PRIMITIVE_TRIANGLES;
cmd.indexCount = indexcount;
cmd.instanceCount = std::max(1, instancecount);
cmd.indexType = getIndexDataType(indexbuffer->getDataMember(0).decl.format);
cmd.indexBufferOffset = startindex * getIndexDataSize(cmd.indexType);
cmd.texture = maintexture;
draw(cmd);
}
void Graphics::print(const std::vector<Font::ColoredString> &str, const Matrix4 &m)
{
checkSetDefaultFont();