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# Plotting f(x,y) = z = min(x,y) creates a 2D-triangle instead of a 3D-surface

By : user6112102
Date : July 30 2020, 11:00 AM
like below fixes the issue They should be surfaces. Your math is right.
Unfortunately, you're plotting two 1-dimensional arrays instead of a 2D array:
code :
``````data_x_axis = list(range(11))
data_y_axis = list(range(11))
X = data_x_axis
Y = data_y_axis
ax.plot_wireframe(X, Y, ....
``````

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## Surface area of projected triangle

By : Rana Harsh
Date : March 29 2020, 07:55 AM
I hope this helps . Project the vertices onto the screen with the model-view and projection matrices from your rendering pipeline Calculate the surface area in 2D with A = sqrt(s*(s-a)*(s-b)*(s-c)) with s = (a+b+c)/2 and a, b, c, the lengths of the three sides of the triangle using some 2D vector math (this is Heron's formula)

## Maximum surface inside a triangle

By : G7duy
Date : March 29 2020, 07:55 AM
Does that help ..answering my own comment/question, it can be proved that the radii must be equal,
Here is a useful formula:
code :
``````A = r^2 ( alpha - Pi + 2/tan(alpha/2) ) /2
``````
``````s = 2 ( b - A/r )
``````
``````ropelength = trianglelength  - 2  Sum[r[i]  a[i]  ]
ropearea = trianglearea -  Sum[r[i]^2  a[i] /2 ]
``````
`````` a[i]=( alpha[i] - Pi + 2/tan(alpha[i]/2) )
``````
``````r =(1/2) (triangle_length - rope_length) /(Sum(1/tan(alpha[i]/2)) - Pi)
``````
``````ropearea = trianglearea - (trianglelength-ropelength)^2/(8 Sum[a[i])
= trianglearea - (1/2)(trianglelength-ropelength)  r
``````
``````Sum(1/tan(alpha[i]/2))  = Sqrt( S^3 / ((S-a)(S-b)(S-c)) )
S = 1/2 (a+b+c)   ! S is semiperimeter not to be confused with arc length s
``````
`````` rinscribed = Sqrt( ((S-a)(S-b)(S-c))  / S )
``````

## Triangle Normal Surface Detection

By : darkguard
Date : March 29 2020, 07:55 AM
I hope this helps . Your approach of testing the normals will still have visual artifacts, because triangles facing the camera could also be obscured. Imagine if that bulge were at the corner closest to the camera.
You will also have triangles that are partially visible and partially obscured.

## Plotting surface in Octave results in non-uniform surface?

By : Jackson Mills
Date : March 29 2020, 07:55 AM
it helps some times Well, as far as I can see in your data X values change every 15 points, so do Y and Z. It seems you are reshaping incorrectly.
Try the next really small changes to your code:
code :
``````xVec = reshape(data(:,1),15,15);
yVec = reshape(data(:,2),15,15);
zVec = reshape(data(:,3),15,15);
surf(xVec,yVec,zVec);
axis([0.15 0.85 0.15 0.85]);
set(gca, 'XTick',0.20:0.05:0.80);
set(gca, 'YTick',0.20:0.05:0.80);
``````

## Do I need triangle information in my surface shader?

By : Ted Dietz
Date : March 29 2020, 07:55 AM
Hope that helps Ok I think I found a solution. Thank you for the comments, they where useful.
Fist I change my grid topology to not use shared vertices. With this I can use a vertex color channel to set the texture ids.
code :
``````vertexColor.r = vertexTextureId0; // Texture to use for vertex 0
vertexColor.g = vertexTextureId1; // Texture to use for vertex 1
vertexColor.b = vertexTextureId2; // Texture to use for vertex 2
``````