As this is company code and part of a bigger framework I can only give
you some hints.
I have a custom shader loader which parses the shader source in order to
later add the defines and creates a osg::Program derived class
e.g. CustomProgram.
In GLSL you can use preprocessor macros like in C.
So you can say:
#define PATH_1
and later
vec4 color = vec4();
#ifdef PATH_1
color = vec4(1,0,0,0);
#else
color = vec4(0,0,1,0);
#endif
So the shader loader will create the CustomProgram which holds a list
of defines which should be applied later.
The CustomProgram itself will do this in the ::apply function, by
injecting the #define %DEFINE_NAME% in to the shadersource before
compiling it.
For setting the defines at the statesets you want, you can simply check
the stateset for a program-attribute, cast it to CustomShader and add a
define.
You will have to do some management inside the CustomProgram to make it
aware of changed define-sets etc. But it the end you are simply adding
some custom attributes to control the compiled shader program at the
state set, instead of setting uniforms directly.
While this seems complicated it allows for two things:
1. Fast less-branching shader code
2. Different sets of shaders realizing rendering based upon defines. In
my case I can do deferred and forward shading with the same framework
without having to know which one is running under the hood, when
assigning materials/material effects.
cheers
Sebastian
Can you please provide an example of how an object manages its define-set?
In my case, I simply get the object's StateSet and setup uniforms. But
I don't get how to setup defines.
Thanks.
2013/11/7 Sebastian Messerschmidt <[email protected]
<mailto:[email protected]>>
Am 07.11.2013 12:55, schrieb michael kapelko:
Hi, Sebastian.
So you compose one shader per object?
No, one program per define-set (e.g. #define
NORMAL_MAPPING,#define PARALLAX_MAPPING, ...)
The idea is not to compose the shader from functional blocks, but
to write one shader containing all paths which are activated based
upon the defines.
It is still complicated to get all the paths correctly in the
ubershader, but i found it a good transition from uniform based
de/activation.
So you will end up with N different programs with N being the
number of define-combinations used.
Thanks.
2013/11/7 Sebastian Messerschmidt <[email protected]
<mailto:[email protected]>>
Hi Michael,
I solved a similar problem by overriding osg::Program which
composes a shader from an Ubershader. This is not done via
uniforms but defines.
It seems to work somehow and improved the performance over
branching based on uniforms.
Hi.
I decided to go with single pipeline that provides big
shaders and objects using own uniforms and textures to
change the pipeline behaviour.
I started to design a simple material format so that it
resembles the one of EffectCompositor.
Thanks.
2013/10/31 michael kapelko <[email protected]
<mailto:[email protected]>>
Hi, Wang.
I've just checked if I can use some uber shader and
control its behaviour per object by setting the object's
uniforms. And it works.
I wonder if that's ok to do that to make different
objects rendered differently in the same scene.
Thanks.
2013/10/31 Wang Rui <[email protected]
<mailto:[email protected]>>
Hi Michael,
Effect compositor in fact adds the child scene graph
to a camera binding to a FBO, and then uses RTT
cameras to perform the post processing work. The
last step is always to show the final image on an
HUD quad so all other scene nodes will be occluded.
The only way to make the effect compositor work with
other fixed pipeline nodes is to write to the depth
values in the shader code of the last step, which
cannot be automated.
The dof.xml does such work so you may try
./osgeffectcompositor --normal-scene cessna.osg
--effect dof.xml to see how normal and deferred
shaded objects are merged. At present I haven't had
a better idea about this problem. :-)
Wang Rui
2013/10/30 michael kapelko <[email protected]
<mailto:[email protected]>>
Hi.
I've recently implemented deferred shading with
normal mapping and shadow mapping using
EffectCompositor, but it has effect on the whole
scene, not a single object.
Is it possible to use EffectCompositor to apply
effects per object?
Thanks.
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