I have OpenGL rendering pipline where each frame has some depth data which is 2D 8bit image. What I need is to:
1) Draw it in realtime with maximum FPS as volume object
2) Map some textute to this object
I think it should be something like this:
[]1
I'm wondering about peformance. Curently I'm reviewing different approaches: building isosurface with marching cubes, raytracing, volume rendering. But still dont sure what is the best approach for this task. I'm using c++, opengl, opencl, glsl.
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I am currently trying to learn ray casting on a 3D texture using something like glTexImage3D. I was following this tutorial from the start. My ultimate goal is to produce a program which can work like this:
My understanding is that this was rendered using a raycasting method and the model is imported as a 3d texture. The raycasting and texture sampling tasks were performed in the fragment shader. I hope I can replicate this program as a practice. Could you kindly answer my questions?
What file format should be used to import the 3D texture?
Which glsl functions should I use in detecting the distance between my ray and the texture?
What are the differences of 3D texture sampling and volume rendering?
Are there any available online tutorials for me to follow?
How can I produce my own 3D texture? (Is it possible to make one using blender?)
1. What file format should be used to import the 3D texture?
Doesn't matter, OpenGL doesn't deal with file formats.
2. Which glsl functions should I use in detecting the distance between my ray and the texture?
There's no "ready do use" raycasting function. You have to implement a raycaster yourself. I.e. between a start and end point sample the texture along a line (ray) and integrate the samples up to a final color value.
3. What are the differences of 3D texture sampling and volume rendering?
Sampling a 3D texture is not much different from sampling 2D, 1D, cubemap or whatever else the topology of a texture. For a given vector A a certain vector B is retured, namely either the value of the sample that's closest to the location pointed to by A (nearest sample) or a interpolated value.
4. Are there any available online tutorials for me to follow?
http://www.real-time-volume-graphics.org/?page_id=28
5. How can I produce my own 3D texture? (Is it possible to make one using blender?)
You can certainly use Blender, e.g. by baking volumetric data like fog density. But the whole subject is too broad to be sufficiently covered here.
I'm working on a visual odometry algorithm that tracks movement of the camera between images. An integral part of this algorithm is being able to generate incremental dense warped images of a reference image, where each pixel has a corresponding depth (so it can be considered a point cloud of width x height dimensions)
I haven't had much experience working with OpenGL in the past, but having gone through a few tutorials, I managed to setup an offscreen rendering pipeline to take in a transformation matrix and render the pointcloud from the new perspective. I'm using VBOs to load the data in the GPU and renderbuffers to render, and glReadPixels() to read into CPU memory.
On my Nvidia card, I can render at ~1 ms per warp. Is that the fastest I can render the data (640x480 3D points)? This step is proving to be a major bottleneck for my algorithm, so I'd really appreciate any performance tips!
(I thought that one optimization could be rendering only in grayscale, since I don't really care about colour, but it seems like internally OpenGL uses colour anyway)
My current implementation is at
https://gist.github.com/icoderaven/1212c7623881d8cd5e1f1e0acb7644fb,
and the shaders at
https://gist.github.com/icoderaven/053c9a6d674c86bde8f7246a48e5c033
Thanks!
I want to render heightmap that are able to deform using latest opengl. What method is recommended for rendering in opengl? Some acceleration method requires that the vertices to be static in order to be stored in high speed memory(gpu mem).
I need a techniques that can exploit gpu features since im rendering huge number of vertices for the heightmap. Before anyone tells me to use LOD, im using LOD already. I want to optimize it.
I'm finding a way to do 3d filters in directx or opengl shaders, same as the gaussian filter for images.In detail, it is to do proccessing for every voxel of a 3d texture.
Maybe store the volume data in slices can do it, but it is not a friendly way to access the volume data and not easy to write in shaders.
sorry for my poor english, any reply will be appreciate.
p.s.:Cuda's texture memory can do this work, but my poor gpu can only run in a very low frame rate with debug model,and i don't know why.
There is a 3D texture target in both Direct3D and OpenGL. Of course target framebuffers are still 2D. So using a compute shader, OpenCL or DirectCompute may be better suited for pure filter purposes, that don't include rendering to screen.
I have been brought in on a project where I need to render a 3D volume from a series of images of the volume. The images have been created by a couple of techniques such that they are vertical slices of the object in question.
The data set is similar to this question, but the asker is looking for a Matlab solution.
The goal is to have this drawing be in something near real time (>1Hz update rate), and from my research openGL seems to be the fastest option for drawing. Is there a built in function in openGL render the volume in openGL other than the following psuedocode algorithm.
foreach(Image in Folder)
foreach(Pixel in Image)
pointColour(pixelColour)
pointLocation(Pixel.X,Pixel.Y,Image.Z)
drawPoint
I am not concerned about interpolating between images, the current spacing is small enough that there no need for it.
I'm afraid if you're thinking about volume rendering, you will need to first understand the volume rendering integral because the resultant color of a pixel on the screen is a function of all the voxels that line up with it for the current viewing angle.
There are two methods to render a volume in real-time using conventional graphics hardware.
Render the volume as a set of 2D view-aligned slices that intersect the 3D texture (proxy geometry). Explanation here.
Use a raycaster that uses programmable graphics hardware, tutorial here.
This is not an easy problem to solve - but depending on what you need to do things might be a little simpler. For example: Do you care about having an interactive transfer function? Do you want perspective views, or will orthographic projection suffice? Are you rendering iso-surfaces? Are you using this only for MPR-type views?