Sign in to follow this  
Hulag

OpenGL Reflections and refractions.

Recommended Posts

Hulag    134
I would like to add support for reflective and refractive objects in my engine. Now, all the stuff I have seen related to reflective oceans and stuff like that but that's easy since its a single plane always pointing in the same direction. What I want is something similar to If you want to see that running download this video (14MB). BTW, I use OpenGL, glSlang for shaders, and I don't have FBO yet but I will very soon.

Share this post


Link to post
Share on other sites
JavaCoolDude    670
You can find some source code and binaries right here.
You can take off the chromatic aberration by refracting your view vector only once and using all of its channels in the final mix.

[Edited by - JavaCoolDude on June 30, 2005 9:15:43 PM]

Share this post


Link to post
Share on other sites
Hulag    134
Quote:
Original post by JavaCoolDude
You can find some source code and binaries right here.
You can take off the chromatic aberration by refracting your view vector only once and using all of its channels in the final mix.

But how does this method work when the shape of the mesh its so different from the shape of a cubemap. For example in the screenshot I posted there are a bunch of reflective and refractive walls which given their shape it wouldn't fit a cubemap so well, how does it deal with that? and from what point should I make the cubemap in that kind of shape?

Share this post


Link to post
Share on other sites
zedzeek    528
u dont need a cubemap for the above image, the refractions are only little.
just grab the background behind the "glassbox" and use that as a lookup with the normals providing the distortion

Share this post


Link to post
Share on other sites
Hulag    134
Quote:
Original post by zedzeek
u dont need a cubemap for the above image, the refractions are only little.
just grab the background behind the "glassbox" and use that as a lookup with the normals providing the distortion

What if the index of reflaction is such that you need to refract to a place that isn't within the view frustum?
Also, what about reflections in those kinds of situations?

Share this post


Link to post
Share on other sites
christian h    200
Quote:
Original post by Hulag
Quote:
Original post by zedzeek
u dont need a cubemap for the above image, the refractions are only little.
just grab the background behind the "glassbox" and use that as a lookup with the normals providing the distortion

What if the index of reflaction is such that you need to refract to a place that isn't within the view frustum?
Also, what about reflections in those kinds of situations?


It seems like ugly hack to do it this way, but this is how it's usually done (since ray-tracing is still far from real-time usage).
You just draw the cubemap from the center of the reflecting/refracting object, with camera that has the same orientation as the object. So it's done in it's local space. Then when you need to render the object, you transform the eye-to-object vector to that object's space and calculate the reflectance and refracting vectors with that to look up in the cubemap.
Whole lotta rendering to do for lots of reflecting objects :(

ch.

Share this post


Link to post
Share on other sites
zedzeek    528
Quote:
What if the index of reflaction is such that you need to refract to a place that isn't within the view frustum?
Also, what about reflections in those kinds of situations?

move the camera :) im not joking
for reflections though youre better served with a cubemap, though in the abovescreenshot there r no reflections

Share this post


Link to post
Share on other sites
Hulag    134
Quote:
Original post by zedzeek
Quote:
What if the index of reflaction is such that you need to refract to a place that isn't within the view frustum?
Also, what about reflections in those kinds of situations?

move the camera :) im not joking
for reflections though youre better served with a cubemap, though in the abovescreenshot there r no reflections

The floor is reflective, and the wall on the right of the 4 cubes thing is also reflective.
Now, the problem I see with cubemaps is reflecting local object, to test that I took JavaCoolDude's example, and replaced the sphere with a big plane and no reflections from the particles showed up, and the refractions where wrong.

Share this post


Link to post
Share on other sites
mikeman    2942
Cubemaps are not good for local reflections. They're good when the reflected objects are supposed to be infinately far away(like a skybox). It can also work to render reflections on small, "closed" objects, but with planes it doesn't work so well.

What you see in the screenshot are just planar reflections and refractions. They get rendered into a texture, and then that texture is projected into the geometry with the texcoords slightly distorted using a normalmap. Not physically correct, but it achieves the desired effect.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Similar Content

    • By Zaphyk
      I am developing my engine using the OpenGL 3.3 compatibility profile. It runs as expected on my NVIDIA card and on my Intel Card however when I tried it on an AMD setup it ran 3 times worse than on the other setups. Could this be a AMD driver thing or is this probably a problem with my OGL code? Could a different code standard create such bad performance?
    • By Kjell Andersson
      I'm trying to get some legacy OpenGL code to run with a shader pipeline,
      The legacy code uses glVertexPointer(), glColorPointer(), glNormalPointer() and glTexCoordPointer() to supply the vertex information.
      I know that it should be using setVertexAttribPointer() etc to clearly define the layout but that is not an option right now since the legacy code can't be modified to that extent.
      I've got a version 330 vertex shader to somewhat work:
      #version 330 uniform mat4 osg_ModelViewProjectionMatrix; uniform mat4 osg_ModelViewMatrix; layout(location = 0) in vec4 Vertex; layout(location = 2) in vec4 Normal; // Velocity layout(location = 3) in vec3 TexCoord; // TODO: is this the right layout location? out VertexData { vec4 color; vec3 velocity; float size; } VertexOut; void main(void) { vec4 p0 = Vertex; vec4 p1 = Vertex + vec4(Normal.x, Normal.y, Normal.z, 0.0f); vec3 velocity = (osg_ModelViewProjectionMatrix * p1 - osg_ModelViewProjectionMatrix * p0).xyz; VertexOut.velocity = velocity; VertexOut.size = TexCoord.y; gl_Position = osg_ModelViewMatrix * Vertex; } What works is the Vertex and Normal information that the legacy C++ OpenGL code seem to provide in layout location 0 and 2. This is fine.
      What I'm not getting to work is the TexCoord information that is supplied by a glTexCoordPointer() call in C++.
      Question:
      What layout location is the old standard pipeline using for glTexCoordPointer()? Or is this undefined?
       
      Side note: I'm trying to get an OpenSceneGraph 3.4.0 particle system to use custom vertex, geometry and fragment shaders for rendering the particles.
    • By markshaw001
      Hi i am new to this forum  i wanted to ask for help from all of you i want to generate real time terrain using a 32 bit heightmap i am good at c++ and have started learning Opengl as i am very interested in making landscapes in opengl i have looked around the internet for help about this topic but i am not getting the hang of the concepts and what they are doing can some here suggests me some good resources for making terrain engine please for example like tutorials,books etc so that i can understand the whole concept of terrain generation.
       
    • By KarimIO
      Hey guys. I'm trying to get my application to work on my Nvidia GTX 970 desktop. It currently works on my Intel HD 3000 laptop, but on the desktop, every bind textures specifically from framebuffers, I get half a second of lag. This is done 4 times as I have three RGBA textures and one depth 32F buffer. I tried to use debugging software for the first time - RenderDoc only shows SwapBuffers() and no OGL calls, while Nvidia Nsight crashes upon execution, so neither are helpful. Without binding it runs regularly. This does not happen with non-framebuffer binds.
      GLFramebuffer::GLFramebuffer(FramebufferCreateInfo createInfo) { glGenFramebuffers(1, &fbo); glBindFramebuffer(GL_FRAMEBUFFER, fbo); textures = new GLuint[createInfo.numColorTargets]; glGenTextures(createInfo.numColorTargets, textures); GLenum *DrawBuffers = new GLenum[createInfo.numColorTargets]; for (uint32_t i = 0; i < createInfo.numColorTargets; i++) { glBindTexture(GL_TEXTURE_2D, textures[i]); GLint internalFormat; GLenum format; TranslateFormats(createInfo.colorFormats[i], format, internalFormat); // returns GL_RGBA and GL_RGBA glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, createInfo.width, createInfo.height, 0, format, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); DrawBuffers[i] = GL_COLOR_ATTACHMENT0 + i; glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + i, textures[i], 0); } if (createInfo.depthFormat != FORMAT_DEPTH_NONE) { GLenum depthFormat; switch (createInfo.depthFormat) { case FORMAT_DEPTH_16: depthFormat = GL_DEPTH_COMPONENT16; break; case FORMAT_DEPTH_24: depthFormat = GL_DEPTH_COMPONENT24; break; case FORMAT_DEPTH_32: depthFormat = GL_DEPTH_COMPONENT32; break; case FORMAT_DEPTH_24_STENCIL_8: depthFormat = GL_DEPTH24_STENCIL8; break; case FORMAT_DEPTH_32_STENCIL_8: depthFormat = GL_DEPTH32F_STENCIL8; break; } glGenTextures(1, &depthrenderbuffer); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); glTexImage2D(GL_TEXTURE_2D, 0, depthFormat, createInfo.width, createInfo.height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depthrenderbuffer, 0); } if (createInfo.numColorTargets > 0) glDrawBuffers(createInfo.numColorTargets, DrawBuffers); else glDrawBuffer(GL_NONE); if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) std::cout << "Framebuffer Incomplete\n"; glBindFramebuffer(GL_FRAMEBUFFER, 0); width = createInfo.width; height = createInfo.height; } // ... // FBO Creation FramebufferCreateInfo gbufferCI; gbufferCI.colorFormats = gbufferCFs.data(); gbufferCI.depthFormat = FORMAT_DEPTH_32; gbufferCI.numColorTargets = gbufferCFs.size(); gbufferCI.width = engine.settings.resolutionX; gbufferCI.height = engine.settings.resolutionY; gbufferCI.renderPass = nullptr; gbuffer = graphicsWrapper->CreateFramebuffer(gbufferCI); // Bind glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo); // Draw here... // Bind to textures glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, textures[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, textures[1]); glActiveTexture(GL_TEXTURE2); glBindTexture(GL_TEXTURE_2D, textures[2]); glActiveTexture(GL_TEXTURE3); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); Here is an extract of my code. I can't think of anything else to include. I've really been butting my head into a wall trying to think of a reason but I can think of none and all my research yields nothing. Thanks in advance!
    • By Adrianensis
      Hi everyone, I've shared my 2D Game Engine source code. It's the result of 4 years working on it (and I still continue improving features ) and I want to share with the community. You can see some videos on youtube and some demo gifs on my twitter account.
      This Engine has been developed as End-of-Degree Project and it is coded in Javascript, WebGL and GLSL. The engine is written from scratch.
      This is not a professional engine but it's for learning purposes, so anyone can review the code an learn basis about graphics, physics or game engine architecture. Source code on this GitHub repository.
      I'm available for a good conversation about Game Engine / Graphics Programming
  • Popular Now