# 3d Definition and 31 Discussions

In 3D computer graphics, 3D modeling is the process of developing a mathematical coordinate-based representation of any surface of an object (inanimate or living) in three dimensions via specialized software.Three-dimensional (3D) models represent a physical body using a collection of points in 3D space, connected by various geometric entities such as triangles, lines, curved surfaces, etc. Being a collection of data (points and other information), 3D models can be created manually, algorithmically (procedural modeling), or by scanning. Their surfaces may be further defined with texture mapping.

View More On Wikipedia.org
1. ### When to consider body fixed reference frame

Hello I am studying mechanics and I have been reading about having the reference frame fixed at a certain point, body fixed and also the gyro equations. I an identify the gyro case easily as I am looking for an AAC body which rotates about an axis. I am confused about the other two cases in...
2. ### I Understanding 3D circle parameterization

Hey I saw this post: https://www.physicsforums.com/threads/general-equation-of-a-circle-in-3d.123168/ trying to understand 3D circle parameterization. I saw the formula given by Hootenanny But I didn't understand it and would like some help. What are u and n and how can I find/calculate them...
3. ### I Equation for circle points in 3D

Hello, I am trying to solve a problem and I would like to ask for help. I have 3 points (A, B, C) in 3D space that are assumed to be on a circle. EXAMPLE 1 EXAMPLE 2 My goal is to create an algebraic formula to calculate the coordinates for 10 points on a circle composed of ABC points at...
4. ### Tetrahedron Simplex Shape Functions in FEA

Hi, 2 part question trying to get tetrahedron Finite Element shape functions working: 1) How do I properly setup the shape coefficient matrix and 2) How do I build the coefficient quantities in the shape functions properly? ANY tips or corrections may unblock me and would be of much value...
5. ### This is a 3D model I made of the Edmund Fitzgerald great lakes ship

These are images of a 3D model I made of the legendary Edmund Fitzgerald, a great lakes bulk carrier ship, which famously sank in lake superior in 1975.
6. ### Film Advance system research for DIY Camera

Dear All, I'm a french professional photographer working on Still Life and Architecture. As a long time and personnal project I'm working on a 3D printed/Laser cut analog camera that will shoot 6x4.5 frames. In the end it will be some kind of rangefinder with integrated electronic light...
7. ### B Do any 3D Venn diagrams exist that have no 2D analogues?

If we were to use three-dimensional spheres to represent sets, could a 3D Venn diagram be constructed that could not be drawn as a normal 2D Venn diagram without changing the relationships between the sets?
8. ### A Packet speed calculation

I've been struggling with the problem below for some time. It is not a homework. A simple bubble S is a spherical surface that expands with constant speed c. A vector bubble V also expands with the same constant speed c. There is a 3d vector associated with a V. If two S bubbles touch, they...

10. ### General solution of the spherical wave equation

Since the spherical wave equation is linear, the general solution is a summation of all normal modes. To find the particular solution for a given value of i, we can try using the method of separation of variables. $$ψ(r,t)=R(r)T(t)ψ(r,t)=R(r)T(t)$$ Plug this separable solution into the...
11. ### Making STRONG shelves with Topology Optimization

A project, that's fun, educational, cool-looking and actually useful! What more could you want? We're making topology-optimized floating shelf brackets today...
12. ### In what direction does a light wave vibrate?

I've wondered this for a while but not known how to ask the question, If light is a transverse wave, then what is it transverse to? To elaborate, light travels in three-dimensions, radially. To me, this seems analogous to the sound wave, with pulses of pressure moving longitudinally to the...
13. ### New metal gear 3D model in Blender

Hi, it's been a long time since I've been on these forums, but here is a new 3D blender model that I spent four weeks of daily work to finish. I'm glad it's done, it wasn't easy. This is metal gear RAY, a 70-foot tall robot from the popular video game franchise metal gear solid.
14. ### I The allowed energies of a 3D harmonic oscillator

Hi! I'm trying to calculate the allowed energies of each state for 3D harmonic oscillator. En = (Nx+1/2)hwx + (Ny+1/2)hwy+ (Nz+1/2)hwz, Nx,Ny,Nz = 0,1,2,... Unfortunately I didn't find this topic in my textbook. Can somebody help me?
15. ### B How do you create a + and π sign using multivariable (x,y,z)

I am taking a high school multivariable calculus class and we have an end-of-semester project where we trace out some letters etc., except that they all have to be connected, continuous and differentiable everywhere. My group's chosen to do Euler's formula, but so far we are having problems...
16. ### 3D file manipulation resources

Hi I am trying to learn how to manipulate 3D files like obj or stl using programming (I primarily use Python, but also know Javascript). Which resources can I use to learn this?
17. ### Which function drawer is this one?

Have anybody seen a 3D function drawer like this one?(4:12) Since I don’t know what these 3D drawers are really called,I can’t find any.
18. ### I Rotation of a point in R3 about the y-axis

Hello, I'm having a visualisation problem. I have a point in R3 that I want to rotate about the ##y##-axis anticlockwise (assuming a right-handed cartesian coordinate system.) I know that the change to the point's ##x## and ##z## coordinates can be described as follows: z =...
19. ### Computer Graphics & More

Hello, I am having trouble comprehending how grids are made and defined in computers. What is the unit that they use and how is it defined ? I know that softwares use standardized units of measure (measurement) such as centimetre. Basically, how is a 3-Dimensional Space created in computers...
20. ### Plot 3D graph of electric potential of a charged particle

Homework Statement Plot the electric potential ##V(r)## due to a positively charged particle located at the origin of an XY plane. Homework Equations ##V=\frac 1 {4πε_0} \frac q r## The Attempt at a Solution I'm unfamiliar with 3D coordinates at this time, but I like to know how can I plot it...
21. ### Find the equation of the plane given point and line (3D)

∴1. Homework Statement Find an equation for the plane that contains the point (1,-1,2) and the line x=t, y=t+1, z=-3+2t? 2. Homework Equations The Attempt at a Solution I don't know what I am doing wrong but everytime I try to do these plane questions my amswer is always the opposite sign...
22. ### Various Properties of Space Curve....*Really *

Homework Statement Let γ : I → R3 be an arclength parametrized curve whose image lies in the 2-sphere S2 , i.e. ||γ(t)||2 = 1 for all t ∈ I. Consider the “moving basis” {T, γ × T, γ} where T = γ'. (i) Writing the moving basis as a 3 × 3 matrix F := (T, γ × T, γ) (where we think of T and etc...
23. ### Finding the curvature of a space curve

Homework Statement Find the curvature of the car's path, K(t) Car's Path: r(t) = \Big< 40cos( \frac {2 \pi}{16}t ) , 40sin( \frac {2 \pi}{16}t ), \frac{20}{16}t \Big> Homework Equations K(t) = \frac { |r'(t)\:X \:r''(t)|}{|r'(t)|^3 } The Attempt at a Solution This is part of a massive 6...
24. ### What variables are needed to find a moment?

Homework Statement You wish to find the moment at the origin produced by a force, ̅F= {Fi}̂, that is applied at r= {̂ai+bj +ck ̂}. Which variables (F,a ,b,c , ) do we need to know to find a numerical answer? Explain using math and figures. Homework Equations Mo = r x F The Attempt at a...
25. ### I Spherical coordinates via a rotation matrix

First, I'd like to say I apologize if my formatting is off! I am trying to figure out how to do all of this on here, so please bear with me! So I was watching this video on spherical coordinates via a rotation matrix: and in the end, he gets: x = \rho * sin(\theta) * sin(\phi) y = \rho*...
26. ### 3D Fourier Transforms?

Hi, I have a FORTRAN code with an array called Chi that I want to run an inverse FT on. I have defined two spaces X and K which each consist of 3 vectors running across my physical verse and inverse space. My code (If it works??) is extremely slow and inefficient (see below). What is the best...
27. ### B 3D models of waves

I am looking for 3D (or 4D, etc.) images of waves (such as light or sound), but seem to be having difficulty locating such models. Can someone please direct me to this kind of display, or is it not something being currently done?
28. ### MATLAB Plotting a 3d function

I had a function of 3 variables f'(kx,ky,kz) and did an ifft f = ifft(f') and now i have a function where inside a small polygon the function f = 1, and outside f=0, within a cube space of length L. how do i plot a scatter graph for this function where there is a point when f =1, and no...
29. ### I How to word a 3D function?

I have, say, an ellipse in the x-y plane: (x^2/a^2) + (y^2/b^2) = 1 I want a 3d (e.g. z) function where inside the ellipse z=+1, outside z=0; the function is not continuous. so in effect what I'm left with is a large plane where z= 0, and a small ellipse cut out raised to z=1. How do I write...
30. ### I Normalizing Constant 3D Infinite Well

For time independent Schrodinger's equation in 3-D Where Enx,ny,nz=(nx/Lx2+ny/Ly2+nz/Lz2)(π2ħ2/2m and Ψnx,ny,nz=Asin(nxπx/Lx)sin(nyπy/Ly)sin(nzπz/Lz) How do I normalize A to get (2/L)^3/2? I don't think I understand how to normalize constants.
31. ### 3D Relativity Question

Homework Statement LOOKING AT PART (c) The ball is traveling at velocity c/√2. The car is traveling at velocity c/√2. Ball is thrown up through the sun roof or something I don't know. Homework Equations The Attempt at a Solution I don't know how to think about this in 3D. I've done parts (a)...