Changing a uniform shader variable on the fly?

[Viking86]

Is it possible, I was planing to combine the slidebar from the tutorial no.5 with a shader. So that when that the user moves the slidebar the parameters of the shader change.

Can this be done?

[Bate]

Of course, just send the value via setPixelShaderConstant or setVertexShaderConstant to the gpu.

[ent1ty]

Some question on not an unrelated note: Can I set the shader constant callback thingy after the new material was with one of the methods in GPUProgrammingServices, or can it be only done when creating the new material type?

[Bate]

Yeah, some kind of setCallback would be nice. I'm using the same material with different callback values for multiple nodes, so at the moment I have to create separate materials (which takes ages to load).

[arras]

What about something like this, wouldn't it help?

Code: Select all

class ShaderMaterialControler : public video::IMaterialRenderer,
                                public video::IShaderConstantSetCallBack
{
   video::IMaterialRenderer *ShaderMaterialRenderer;
   const video::SMaterial *Material;

public:

   ShaderMaterialControler(video::IVideoDriver *driver, const c8 *vertexShaderFilename, const c8 *fragmentShaderFilename, s32 &materialID, const c8 *materialName)
   {
      video::IGPUProgrammingServices *services = driver->getGPUProgrammingServices();

      s32 mID = services->addHighLevelShaderMaterialFromFiles(
         vertexShaderFilename, "main", video::EVST_VS_1_1,
         fragmentShaderFilename, "main", video::EPST_PS_1_1,
         this, video::EMT_SOLID);

      materialID = driver->addMaterialRenderer(this, "materialName");

      ShaderMaterialRenderer = driver->getMaterialRenderer(mID);
   }

   virtual void OnSetConstants(video::IMaterialRendererServices* services, s32 userData)
   {
      video::IVideoDriver* driver = services->getVideoDriver();

      if(driver->getDynamicLightCount() > 0)
      {
         u32 type = (u32)Device->getVideoDriver()->getDynamicLight(0).Type;
         services->setVertexShaderConstant("LightType0", (f32*)&type, 1);
      }
      if(driver->getDynamicLightCount() > 1)
      {
         u32 type = (u32)Device->getVideoDriver()->getDynamicLight(1).Type;
         services->setVertexShaderConstant("LightType1", (f32*)&type, 1);
      }
      if(driver->getDynamicLightCount() > 2)
      {
         u32 type = (u32)Device->getVideoDriver()->getDynamicLight(2).Type;
         services->setVertexShaderConstant("LightType2", (f32*)&type, 1);
      }
   }

   void OnSetMaterial(const video::SMaterial& material, const video::SMaterial& lastMaterial,
      bool resetAllRenderstates, video::IMaterialRendererServices* services)
   {
      Material = &material;
      ShaderMaterialRenderer->OnSetMaterial(material, lastMaterial, resetAllRenderstates, services);
   }

   bool OnRender(video::IMaterialRendererServices *services, video::E_VERTEX_TYPE vtxtype)
   {
      return ShaderMaterialRenderer->OnRender(services, vtxtype);
   }

   void OnUnsetMaterial()
   {
      ShaderMaterialRenderer->OnUnsetMaterial();
   }

   bool isTransparent()
   {
      return ShaderMaterialRenderer->isTransparent();
   }

   s32 getRenderCapability()
   {
      return ShaderMaterialRenderer->getRenderCapability();
   }
};

[Viking86]

Thank you, I made it like this
declare a global variable for the parameter
pass that variable as a uniform to the shader

Make an event receiver in which key presses modify the global variable.
Voila