Questions tagged [3d]

Questions and problems dealing with three-dimensional space, including 3D meshes and other data structures, vector math, transformations, etc.

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49 views

What is the reason that a boolean operation between two almost identical 3D triangular meshes fails?

I have been trying to detect defects on "before-and-after" meshes, by finding the boolean difference between them, to no avail. I tried these two Python libraries(algorithms run in C++) but their ...
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2answers
33 views

glBindImageTexture returning INVALID_VALUE

I am currently having an issue with OpenGL as I am trying to load some vector information into a 3D texture. Currently, I am developing in OpenGL 4.6 which should support Image bindings. this my ...
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41 views

Mathematics in Computer Graphics

Can you please recommend some topic for research work related to mathematics in CG? (Maybe something like "Affine transformations in CG")
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1answer
38 views

Keep constant number of visible circles in 3D animation

I have created a 3D animation with a perspective projection of white circles moving randomly in a fake 3D space projected on a 2D computer screen (GIF 1). Since I need to keep the same number of ...
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1answer
24 views

Looking for a compact file format for outputting 3D geometry with color support

I am looking for a file format to output some 3D geometry. In my case, it only needs to handle very simple shapes - uniformly spaced and sized cubes at points in space. So far I've ended up just ...
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28 views

constant pixel width for any scale

I have a standard 3d camera/projection/model setup that renders rectangles with a WebGL shader. Users can zoom out and fly anywhere. I want to make sure that regardless of the scale, width of the ...
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1answer
67 views

Graphics engines during the sixth console generation

From my understanding game developers used mostly proprietary, in-house graphics engines during the sixth console generation (Xbox, PS2, GC, DC) on a game to game basis. Why didn't standard engines ...
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49 views

What is it that really prevents photo-realistic, real-time, digital 3D simulations?

Ever since I was a small child, seeing the amazing 3D visuals that developed in the 1980s and 1990s, I was certain that photo-realism was "just around the corner". In the year 2020, I certainly ...
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1answer
73 views

Defining “inside” and “outside” of a 3D space

I am not sure if this is the correct SE to ask this question. However, lets say I have been given 3D models of several enclosed spaces. I want to populate spaces with, lets say, planes flying through ...
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15 views

Turning layered curves to polygon mesh?

I am confronted with the problem to render 3D representations for objects marked on microscope slices. So I have a set of aligned polygons in parallel planes from tracing the outline of the object in ...
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2answers
42 views

Y axis inversion in 3D rasterization

What is the correct way to invert the y axis during the 3D projection? I see a lot a people doing: ...
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27 views

After making any 3D model using Opengl how to export it's data in .dae file?

I'm trying to make simple 3d modeling program in c++ with Opengl. So I don't know how to transfer/convert/export or save data of 3D model in .dae file. NOTE:- 3d model is made using Opengl ...
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Intrinsic Matrix vs Perspective projection matrix

I was going through the camera matrix explained in the wikipedia article and understand how the matrix K \begin{bmatrix}f_x&s&x_0\\0&f_y&y_0\\0&0&1\end{bmatrix} is built. The ...
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46 views

Estimate 3D cube pose after camera rotation

I have some photos of 3D cube. I also know the 3D pose of the cube in each photo (yaw, pitch, roll). I want to estimate the new pose (yaw, pitch, roll) of the cube after performing 2D rotation to the ...
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1answer
42 views

Understanding the near clipping plane

I don't understand something about the near clipping plane. It's there to avoid the division by $0$ but when we compute the pixel coordinates, we just need to multiply by the clipping plane to clip ...
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0answers
75 views

BSP tree rendering

As a little project, I'd like to implement a BSP merging algorithm for Boolean operations on solids. But to even tell whether it works, I need some way to render the BSP tree. In other words, I have a ...
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2answers
195 views

What are “Triangles” in 3d modeling?

In 3d modeling, there is some "triangle count" which determines complexity. I am not sure but I think cubes have 12 triangles or somethong. But I see NONE. They have squares, no triangles! Can someone ...
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1answer
73 views

How can I raycast with chunks?

I am attempting to implement chunks/octrees to speed up my render times. However, sometimes the walls show horizontal or vertical lines (rays hitting the inside of voxels?) or some blocks disappear ...
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1answer
53 views

Why is the z direction away from the screen/viewer?

I wonder what is the reason that when z increase, the objects appear far away and when z is negative, the object is behind the camera?
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2answers
63 views

Visualize the interpolated unit quaternion on the surface of the unit sphere

My major is mechanical, please forgive me for asking questions that may seem trivial to you. First, I'm reading the following paper: Dam, Erik B., Martin Koch, and Martin Lillholm. Quaternions, ...
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1answer
73 views

Compute Speed of Spheres in 3D animation

I have created two animations: One where a "camera" moves towards the spheres creating an optic flow (1st GIF).The code can be found here. One where spheres move randomly in a 3D coordinates space (...
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1answer
155 views

Rendering equation for spherical lights

I am currently implementing spherical lights in my DirectX game engine. I decided to build the shading formula from the classical rendering equation. Here is what I get: The simplifications show that ...
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0answers
20 views

Apply a pose to a 3D model/mesh

Assuming that I have pose information for a human, is there any ways/tools to apply that pose to a 3D model? Basically, given continous pose information say from a dancing person, I like to animate a ...
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1answer
37 views

Calculating normals for vertices which aren't a vertex of all neighbouring triangles

In my procedurally generated mesh in Unity, not all vertices are vertexes of all neighbouring triangles - essentially, it's a grid with cells of varying sizes. This is messing up the calculation of ...
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22 views

Is it possible to set visible and color for all 12 edges(spines) of the figure (cube) in matplotlib?

In 2d, matplotlib plots all 4 edges(spines) of a figure. In 3d, matplotlib plots 9 out of 12 edges of a cube. Is it possible to set visible and color for all 12 edges(spines) of a cube in 3d? I ...
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1answer
45 views

Why does my code generate a figure whose kurtosis looks a little higher than the one I am trying to reproduce?

this figure (fig_1) is an univariate normal distribution in 3D, the corresponding equation is in the top left hand corner it seems that x varies from -5 to 5; sigma varies from 0 to 4. This Python ...
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1answer
42 views

Why does my code to plot a cone actually generate a roof?

per this post, this formula $Z = 1 - \sqrt{X^{2} + Y^{2}}$ generates a cone where the point is at (0, 0, 1) and it spreads out below that. It meets the x-y plane at the unit circle I am trying to ...
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1answer
83 views

Could some give an explanation or hint about this kind of equation? $\left(- \sqrt{X^{2} + Y^{2}} + 1\right) \cos{\left (2 \pi X + \phi \right )}$

This is a screen shot from an animation generated by a matplotlib example the key part in the code is ...
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2answers
72 views

Creating a Smooth 3D Mesh from a 2D Outline

I am trying to find (or maybe create) an algorithm for creating a smooth, rounded 3D mesh given a 2D outline. I'm trying to recreate a system from a Gamecube game called Amazing Island, and you can ...
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1answer
606 views

What's the difference between Clipping and Culling?

In a tutorial about OpenGL both words are mentioned, unfortunately without a good explanation. To find out, I have read this article three times, but I fear I'm a too common man... my understanding is ...
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1answer
107 views

Calculating the angle between two polygons

For my application, I want to render models as polygonal surfaces in 3D space and have edges that are bent "outwards" to have a solid line and those who are bent "inwards" to have a dotted line. So if ...
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1answer
57 views

What is performance better - add four materials to mesh or duplicate every vertex and use packed texture?

I am making ski jumping game (in Unity) with procedurally generated hill mesh. I want to add lines on hill like this (mesh is created by script, but I've manually assigned materials in Blender) ...
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0answers
14 views

How can I detect if an edge has flipped during the UV unfold process?

I'm writing my own UV Unfold operation (similar to Maya's Optimize UV tool or 3DS Max's Relax Tool). My code works great 90% of the time but in some instances, I'm getting faces and edges that flip ...
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0answers
112 views

Help with understanding the look-at function (the view matrix)

I've been reading this article about the look-at function. I don't understand the part when they're trying to inverse the matrix N. They say that R is orthogonal because all its row and column ...
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2answers
441 views

How can i wrap the earth image around a 3D Sphere using OpenGL, GLFW, GLAD, GLM?

Please help me out with this thing and currently i am a little more than a beginner so please tell me in that context. i don't need any obsolete methods for creating this like using GLUT or GLEW.can ...
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1answer
310 views

What are the i,j,k components of a 3d mesh on plot.ly (online)?

A 3d Mesh on plot.ly online graph maker (https://plot.ly/create/#/) takes 3 mandatory variables (X, Y, Z) and 3 optional variables (I, J, K). I understand that if I want to draw a cube that I then ...
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0answers
20 views

Newby - which computer language for video to video &/or 4-D to video

First post on forum. What's the simplest language / package for computer graphics that will do what i need? I have two projects in mind: One is to input a video (eg. from youtube) and process it ...
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0answers
88 views

Why don't I see tile-based 3D graphics?

As we know, tiles can make it quicker to update large portions of the display at once, as compared with a bitmap. To put, say a letter, on the screen, the Commodore 64 typically does two writes (the ...
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2answers
600 views

Programmatically generating bin files for GLTF models

I have a need to generate a series of GLB files. I have a base template for a GLTF file which I have to derive off of. The models thus generated will only have varying textures on them. The base mesh ...
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0answers
98 views

Using octree for cheking intersection of ray and meshes

I wrote the code for checking intersection of ray and meshes on scene. It consist of two parts - broad phase and narrow phase. In broad phase I build an oriented bounding box around each mesh and ...
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1answer
416 views

Vulkan: efficient way to update VBO mesh vertices?

I would like to change/add/remove some mesh vertices in existing VBO's (while deforming and remeshing 3D objects) . With OpenGL I would have to reload whole vertex VBO's. I suppose with Vulkan there ...
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0answers
67 views

Programmatic rendering of 3D animations

Many years ago I used POV-Ray to render some 3D animations. I liked POV-Ray's Scene Description Language (SDL) as I could generate the required files programmatically using other languages (e.g. Perl)...
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2answers
374 views

Unfold a 3D mesh to a 2D plane

I'm trying to unfold a 3D mesh onto a 2D plane. My general idea to do this, would be to cycle through all the faces of the meshes and perform a hierarchical transformation. So I would start at the ...
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1answer
173 views

Rendering 3-D point clouds obtained from depth maps as a 2.5D video

Suppose I have code to generate a bunch of frames, each of which is a depth map(I have access to the matrices which represent depth) which in turn is used to generate a point cloud. One frame would ...
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1answer
151 views

Why do animated CG characters always feel fake?

Why do animated CG characters always feel fake? Usually if a CG character is an animal (or humanoid creature), they tend too look kinda off. Their movement tends to look oddly smooth or lightweight, ...
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2answers
184 views

transformation from cartesian coordinates to spherical coordinates without calculations

Given this graph in the 3d cartesian coordinates i should figure out the spherical coordinates representation but without the use of calculations . I've been trying to solve this the whole day but i ...
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1answer
29 views

Can you generate your own HDRI maps without using photos?

For example, preparing a scene in Maya using standard lights and rendering out a panorama? Could they also be made from scratch in photoshop using 32bit color? Is there a reason why people don’t ...
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0answers
56 views

Intersecting Frusta

I am trying to determine whether two frusta intersect in 3D space and to quantify this intersection as a percentage of one frustum volume (eg. 100% intersection meaning that the two frusta occupy the ...
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1answer
80 views

If you can use subdivision surfaces for 2D curves

I've seen how subdivision surfaces are good for 3D curves/modeling, but haven't seen anything on if it's good, or even usable, in 2D. My question is just that, if (a) you can even use subdivision ...
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1answer
142 views

Problems with Subdivision Surfaces

It sounds like Subdivision Surfaces are better than NURBS but not as good as T-splines. I would like to know some of the disadvantages of Subdivision Surfaces, what they can't do or what they do ...

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