Is there a way to display the colored x,y,z crosshairs that are visible in the 3D volume view in 2D slices (like in lesson 13)?
Thanks!
Nolan
the crosshairs are just borders around the slices. What do you have in mind to display them in 2D?
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In the 2D renders, such as in Lesson 13 (http://lessons.goxtk.com/13/), is it possible to add a crosshair cursor indicating the position of orthogonal slices, like this sample?
Furthermore, is it possible to show that crosshair in the 3D volume render, instead of showing three orthogonal slices?
In my case I wanna render 50,000 or more cubes that are distributed randomly inside a large bounding box, I don't want using instancing right now so I have to render each cube, I wanna improve the performance by culling out the cubes that are outside the camera view.
I have a camera class that has two matrices view and projection, each cube has its own bounding box, so I am planning to check each frame if the camera view bounding box contains the center of each cube if yes call its draw function if not ignore it.
I have for view matrix 3 vectors eye, target and up, and for projection width, height, near, far and FOV.
so I have two questions:
Is this a right scenario? I will calculate the camera view boumding box each frame then test each cube.
How can I calculate the camera bounding box each frame?
I got an idea from here how_to_check_if_vertex_is_visible_for_user that worked fine with me.
multiplying the projection view matrix of the camera by the any point in the 3D space the visible ones should be between [-1,1].
I am trying to implement an overlay for a particular screen saver that I inject my application into.
This screen saver uses 3d objects and a dynamic camera.
I have camera position and direction and the 3d object positions, and the fov value, and I'd like to create an audio based overlay that adds icons to the objects.
I have the 2d overlay in place, and can successfully iterate the objects, however I can't figure how to calculate a frustum with the data I have.
Basically: how can one create a frustrum from the camera direction? Is a world to screen matrix required to create the frustum? I don't have the w2s matrix, so would that make the problem impossible to solve?
There is an excellent resource at http://web.archive.org/web/20120531231005/http://crazyjoke.free.fr/doc/3D/plane%20extraction.pdf which should explain everything you need and outlines how to extract the view frustum using the view and model matrices.
In regards to the world to screen (W2S) matrix you can calculate it on the fly by utilising a variant of the following:
ScreenPosition = (ProjectionMatrix* (ViewMatrix * WorldPosition))
Thast way you can calculate it on the fly as required.
There is also a frustum tutorial at Lighthouse aimed at frustum culling, but explaining the implementation quite nicely.
Given a sphere like this one from google streetview.
If i wanted to create 4 views, front view, left view, right view and back view, how do i do the transformations needed to straiten the image out like if i was viewing it in google streetview. Notice the green line i drawed in, in the raw image its bended, but in street view its strait. How can i do this?
The streetview image is a spherical map. The way streetview and Google Earth work is by rendering the scene as if you were standing at the center of a giant sphere This sphere is textured with an image like in your question. The longitude on the sphere corresponds to the x coordinate on the texture and the latitude with the y coordinate.
A way to create the pictures you need would be to render the texture as a sphere like Google Earth does and then taking a screenshot of all the sides.
A way to do it purely mathematical is to envision yourself at the center of a cube and a sphere at the same time. The images you are looking for are the sides of the cube. If you want to know how a specific pixel in the cube map relates to a pixel in the spherical map, make a vector that points from the center of the cube to that pixel, and then see where that same vector points to on the sphere (latitude & longitude).
I'm sure if you search the web for spherical map cube map conversion you will be able to find more examples and implementations. Good luck!
Any good references on displaying sequence of images from a video as voxel data in OpenGL? I want to display all these images at once as a cuboid with 50% alpha and navigate using keyboard or mouse.
Check out this tutorial on setting up a 3D texture.
If you then render slices through the texture array with the appropriate UVW coordinates you will get what you are after.