Project from View distorts texture along triangle edge

Hi, I want to map a texture on a 3d-dimensional object with “Project from View”. However, I noted that - although I don’t use triangles but only quads - the texture is somehow distorted along the inner edge of the quads that divides them into triangles:

I did the following:

Enter Edit mode for the object
Hit U
Select Project from View

I created a new material and selected this texture for it

I am using the Blender Renderer in Blender 2.74.

Does anybody has an idea how to solve this problem?

ok, is there any solution for this problem in Blender? I don’t want to move the vertices manually in the UV editor. I just would like to have an adequate projection mapping for a certain perspective. I thought, this is the purpose of the “Project from View”-function!?

Try subdividing mesh

This doesn’t solve the problem of the non-affine transformation but for practical purposes this works quite well. Thanks for the tip!

But nevertheless I am surprised that you can’t use a transformation that takes the quad into account and not the triangles.

can you upload sample file with images pack!

I think it is doing what it should be but if you project on angled faces and you look at it at different angle
it might look distorted but this is how projection works !

happy bl

here is a sample blend-file that describes the problem. note the distortions in the cube.

test.blend (416 KB)

The problem is not the distortion which you can see from different angles but those one that are caused by the triangle-representation of the quads (see first picture, where I used the view to project the uv-map)

I think it depends on how you unwrap it and also render it
I mean at what angle !

did a test with 2 render different angles

if you don’t want any distortion then use camera or global mapping may be

happy bl

what did you do? did you pressed ‘u’ and ‘Project from View’. Did you subdivide the mesh?

Have you looked into the test-file and saw what I mean?

Try using “Project from View” (PFV) from any orthographic view, not a perspective one:

Left: PFV in orthographic view / Right: PFV in perspective view

PyroGXPilot so in orthographic view it works as expected but in perspetive view not. thanks for the hint. of course, if I would like to use animations and the illusion of a 3d scene I would like to use perspective view.

so the basic problem is, that the mapping of the uv-grid on the 3d surface is based on triangle faces and not quad faces (as outlined in the link by PyroGXPilot. Any ideas, whether this behavior can be changed?

You only need to be in orthographic view for the “Project from View” - after that you’re free to return to perspective view…

yes, but then the illusion does not work in perspective view

been told before when u use project it is function of the camera view

if u don’t want the change function of the view then use Camera or global mapping !

happy bl

But nevertheless I am surprised that you can’t use a transformation that takes the quad into account and not the triangles.

This is a serious issue in any of the 3d apps I tried.
There are not quads for a render engine, only tris.
The bitter truth.
Not particularly a blender issue.

  1. Maybe subdivide a lot (simple subs) and bake the texture?
  2. Maybe export the UV layout as image and try to transform the texture in Pshop/gimp ?
    I think, the second workaround will work better. Actually, I have seen some addon on another app (3dmax,maya) which work on this basis. Transform the texture instead the mesh or the UV island.

Try screen/window mapping, i the texture has to be always aligned to the screen.

Your best chance is to bake a subdivided (simple) mesh with follow active quad Unwrapping into a non dubd version with a second standard UV unwrapping.
(save the texture !!! and re open the blend file (hmmm found a bug here, irrelevant to the thread, I’ll report it)

Here a 6 faces mesh. No distortion though.

I made an experiment in cycles and it worked ok… I tried to reproduce the same thing in BI, but wasn’t able to get the correct results from baking.

here are my steps for Cycles:

  • place your camera(projector) and setup the render width and height to macht your texture file.

  • Unwrap your object. (it can be as you’ve done in your first post)

  • Create a destiny texture in the UV editor.

  • Create an emission material with two textures (the projection and the destination textures) and a Texture_Coordinate node.

  • connect the ‘Window’ vector into the projection texture, and its output to the emission.

  • Bake emission and save the resulted texture.

thanks michalis and secrop for your ideas. I think these are the best workarounds to achieve a correct projection mapping.