23
votes
Get vector length with GLM
Sorry folks for posting such a trivial issue! The issue is solved. I was using the wrong function. Here goes the correct one:
...
- 1,229
9
votes
What is the difference between a point transformation and a vector transformation?
Here's the simple answer.
In 4D, to be able to multiply them by a 4x4 matrix, vectors are represented as (x,y,z,0) and points are represented as (x,y,z,1).
Since the 4th row of a 4x4 matrix ...
- 7,751
6
votes
Accepted
Graphics Pipeline: Viewspace & Back face culling incorrectly
I (believe) I've solved this (even if it has taken 2 days). My problem was essentially I wanted to take the dot product of the face normal, and line-of-sight vector like below
And determine the angle ...
- 243
6
votes
Ray tracing with thin lens camera
In a traditional camera, the photons from the scene travel through the lens of the camera, then hit the sensor at the focal length. A consequence of the lens is that the image is upside down and ...
- 3,732
5
votes
Test if a point is on a line segment
Let's say you have your two points that define the line segment: $A$ and $B$, and a point $P$ that you are testing to see if it is on the line segment.
Firstly, you get a normalized vector from $A$ ...
- 7,751
5
votes
Accepted
Interpolating vectors on a grid
I did some research and found the answer I was looking for. The three most common ways to interpolate vectors are:
Slerp - short for "spherical interpolation", this is the most correct way, but is ...
- 7,751
4
votes
Accepted
Calculating the angle between two polygons
I suggest computing the normal vector for each polygon and compute the angle between the normal vector of one triangle and the normal vector of a plane perpendicular to the other surface that passes ...
- 410
4
votes
Correct view-space transform
I've done some small changes to how I usually construct my view matrix, here is what I've modified:
...
- 141
4
votes
Accepted
Normal vector in Phong Illumination Model should be normalized?
Short answer: yes.
Longer answer: yes, because the vectors you’re using are meant to represent directions, not directions-and-distances. Think of it in terms of light: it doesn’t matter how far a ...
- 2,132
4
votes
Accepted
Video-games; Rendering textures on scope zoom-in. Texture compression problem?
Well there's no way to know for sure unless you look at the source code but my guess is that they do zooming by lowering the FOV (field of view) of the camera. This is easy to implement and actually ...
- 296
3
votes
Accepted
Vector Math for Raytracer
I think there might be a misprinting in the book. I am getting this
$((A-C) + tB)\cdot((A-C) + tB) = R\cdot R$
Let A-C = Y
$(Y + tB)\cdot(Y + tB) = R\cdot R$
$...
- 2,393
3
votes
Accepted
Perlin Noise with Smooth function vs Lerp
It looks like the way you're using smoothstep isn't quite right.
With lerp, the first two parameters are the endpoints of the output range, and the third is a 0–1 value specifying how far to ...
- 24.8k
3
votes
Can somebody explain this Ray Tracing Function?
Good answer above. (I like that the book adds in p then subtracts it.)
This is a hard-coded grey world as a "hello world" kind of ray tracer. The 0.5 is the hard-coded reflectance. Keep ...
3
votes
Creating vector shapes using only C++
What you are looking for is a way to get access to individual pixels in an image, in a way that you can modify those pixels with CPU code.
Once you have that you'll want to find software rendering / ...
- 7,751
2
votes
Accepted
Can somebody explain this Ray Tracing Function?
vec3 target = rec.p + rec.normal + random_in_unit_sphere();
return 0.5*color(ray(rec.p, target-rec.p), world);
this is the exact same as
...
- 5,920
2
votes
What is the difference between a point transformation and a vector transformation?
If you would look up the definition of a vector and a point, then a vector is:
A quantity, such as velocity, completely specified by a magnitude and a direction.
http://www.thefreedictionary.com/...
- 1,595
2
votes
Where should I project a polygon corner when it is behind me?
Trying to explain a problem seems to help the thought process. This is what eventually worked for me:
I realized that I can easily find the point (in 3D space) where a line between two of the corners ...
2
votes
Accepted
Finding the normals of a tileable 2D surface extracted from 4D space
Since the question was somewhat clarified I will formalize both the question and the answer for future readers.
Having a differentiable scalar field $f : \mathbb{R}^4 \rightarrow \mathbb{R}$ we want ...
- 2,083
2
votes
Accepted
Refraction: given an incoming and transmitted direction, can I deduce the normal?
See equation (16) in Microfacet Models for Refraction through Rough Surfaces : $-(\eta_i w_i + \eta_o w_o)$ which you'll probably want to normalize. $\eta$ are the two indices of refraction and $w$ ...
- 1,585
2
votes
Accepted
Plotting points along a 3D line segment
You shouldn’t need to use any trigonometry here at all. If you get the vector from v1 to v2 and divide it by the number of points you want along the line, each subsequent point is v1 + (that vector) × ...
- 2,132
2
votes
Help understanding tangent from dot product and max distance from component wise vector multiplication
There is very little geometrical meaning to the multiplication of two vectors and there are no well defined identities describing the result. But that doesn't make it illegal, and is an important part ...
- 3,030
2
votes
Accepted
Trouble transforming vectors from view space to screen space using a perspective projection matrix
The way to do the projection is the following:
...
- 1,136
1
vote
Extending an orthogonal set of vectors (graphics application?)
The most common use is almost certainly computing normal vectors for a surface, using a cross product. Although strictly speaking, this does not quite qualify as the two initial vectors are usually ...
- 1,585
1
vote
3d Math Primer book equation derivation - Projecting One vector onto another
Since we have:
$$\pmb{v}_{\parallel} \parallel \pmb{n},$$
then:
$$\pmb{v}_{\parallel} = k\pmb{n}$$
We want that the length of $\pmb{v}_{\parallel}$ is $\|\pmb{v}_{\parallel}\|$, then:
$$\|\pmb{v}...
- 2,083
1
vote
Accepted
3d Math Primer book equation derivation - Projecting One vector onto another
Since v∥ is parallel to n, it can be expressed as some multiple of n. The multiple is the ...
- 2,132
1
vote
Morph Targets Normal adding math
It would seem that, in the second example, the morphNormals are targets while in in the first they are deltas.
This explains the difference in math used between the two pieces of code.
- 156
1
vote
How do I derive this transformation
I'm not going to dive into much details about affine transformations and such, you are better off reading up on these concepts from good graphics books.
I think The matrix you need is this.
$\begin{...
- 2,393
Only top scored, non community-wiki answers of a minimum length are eligible