OpenGL shaders with derivatives cause fatal errors (using shader profiles higher than 1.0) about bgfx HOT 6 OPEN

The fix appears to be in shaderc.cpp, where the logic to append precision should exist much further down

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Provide shader source that has this issue.

from bgfx.

Any shader that uses dFdx or dFdy, for example you could try adding something like this to one of the shaders:

float textureMipLevel( sampler2D tex, vec2 uv )
{
	// Estimate using OpenGL spec: http://www.opengl.org/registry/doc/glspec42.core.20120427.pdf
	vec2 texel = vec2( textureSize( tex, 0 ).xy ) * uv;
	vec2 dx_vtc = dFdx( texel );
	vec2 dy_vtc = dFdy( texel );
	float delta_max_sqr = max( dot( dx_vtc, dx_vtc ), dot( dy_vtc, dy_vtc ) );
	return 0.5 * log2( delta_max_sqr );
}

But there isn't much need, the issue starts at line 2373 of shaderc.cpp, where precision is injected before many other extensions. The same problems would occur with GL_EXT_shader_texture_lod, GL_OES_texture_3D and so on.

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See example 42-bunny...

Type make TARGET=4 rebuild, and there is no issue.

from bgfx.

Did you use target profile 310_es or 320_es? It won’t occur for 100_es due to the logic surrounding precision injection in shaderc.cpp

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Target 4 will build glsl, for android gles it is:

make TARGET=3

And the parameter to shaderc would need to be -p 300_es, so in my makefile I have something like:

ifeq ($(TARGET), 3)
VS_FLAGS=--platform android -p 300_es
FS_FLAGS=--platform android -p 300_es
CS_FLAGS=--platform android -p 300_es
SHADER_PATH=shaders/essl

Which should be fine since the default for BGFX_CONFIG_RENDERER_OPENGLES_MIN_VERSION is 30.

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