Go Back   AC3D Forums > Resources > AC3D Tutorials and How-To's
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Display Modes
Old 12th October 2007, 02:02 PM   #1
ggunners
Junior Member
Junior member
 
Join Date: Oct 2007
Location: Chantilly, VA
Posts: 7
Default How to texture map a cone shape

Hello all!

I have got general texture mapping down pretty well but am having problems with mapping a spiral to a cone shape for the propeller spinner on a model airplane.

I ended up just putting alternating stripes down the spinner, selecting circles of points and rotating each segment of the spinner around the center axis. This creates a lot more polygons.

I also tried creating a flat yellow spiral on a black background and mapping it to the front of the cone, but while looking great from the front, it did not look like a spiral from the side.

Spherical mapping looks very weird on the image map so I didn't use it.

The only other option I could think of is to use UV mapping but wasn't sure what that meant. It seems to indicate you need a seperate image map for the UV mapping and then I wasn't sure the kind of flat projection you need to create a spiral on a cone.

Any ideas?

-- ggunners
ggunners is offline   Reply With Quote
Old 12th October 2007, 05:38 PM   #2
lisa
Senior Member
Professional user
 
lisa's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 917
Default Re: How to texture map a cone shape

What's your target poly count?
lisa is offline   Reply With Quote
Old 12th October 2007, 07:18 PM   #3
lisa
Senior Member
Professional user
 
lisa's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 917
Default Re: How to texture map a cone shape

I just re-read your post....

So for clarification, you want to put a spiral on a simple cone--as few faces as possible, no extra divisions--and avoid the warping along the sides?

Normally I'd recommend to you exactly what you already said you tried, to lay the map down in stripes and rotate the points. BUT... if that's too many polys, there is an alternative, but it's a bit tricky.

What you need to do is "bake" the conic projection into your map. You can use POV-Ray to do this.

In a nutshell, with the number of vertices and the type of map you want, there is *no* simple projection that will not have warping. What you really want is a conic projection, but it needs more points to hold up. So, if you can't get rid of the warping in the UVs, the way you fix it is to introduce the opposite warping to the texture. That way, when you apply it, the two distortions cancel each other out and you get exactly the map you wanted.

Here's an example of a sky cube with a spherical warp, so you can see what I mean. This distortion lets me apply what was previously an ordinary cube to a spherical environment map:



A better view, as a checkerboard so you can see what's going on:


To do this in POV, you need to either set up a camera with the projection you want--this is easy for spherical projections, I've never tried a conic projection but I am certain it's much harder to do--or create two versions of your object: a high-resolution version with exactly the UVs you wish you had, and a second object that is geometry built out of the UVs of the first. You then render from the first to the second to transfer the texture to the new UV map.

Since I know what I just said was probably impossible to follow , here's a picture:



You can use the UV to DXF plug-in I put up on my blog the other day to extract the texture coordinates to geometry: http://independentdeveloper.com/arch..._uv_map_to_dxf
lisa is offline   Reply With Quote
Old 13th October 2007, 10:45 PM   #4
ggunners
Junior Member
Junior member
 
Join Date: Oct 2007
Location: Chantilly, VA
Posts: 7
Default Re: How to texture map a cone shape

lisa, thanks for the reply.

The UV mapping projection sounds more difficult than just applying the stripes and rotating the disks. Surface counts were 48 for a conical shape without a spiral stripe and 288 surfaces for the more complex but more accurate version. Here's some pictures showing the image map problem and what I'm using now.

I thought I might take the object I created and flatten it out to see if there might be an easier way to map it. Meanwhile, the straight lines and rotating disks using points works OK.

Thanks again.

-- ggunners
Attached Thumbnails
Click image for larger version

Name:	conical-mapping-1.jpg
Views:	387
Size:	69.3 KB
ID:	515  

ggunners is offline   Reply With Quote
Old 14th October 2007, 04:35 PM   #5
lisa
Senior Member
Professional user
 
lisa's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 917
Default Re: How to texture map a cone shape

It is a little tricky to setup, although thankfully you only need to do it once--you can reuse the same projection file over and over to project as many textures as you need.

Hmmm. I think you can get away with less surfaces if you try UV mapping to a disk *before* making it into a cone. Add concentric rings to the disk using divide loop, then move and rotate by fixed increments.

Also, make sure the stripes on your texture line up with the vertices on the map, if possible. That should also make it smoother.

Here's my test at 180 and 48 surfaces respectively, and my map. The 180 surface cone is a subdivision of the 48 surface cone. I haven't tried it, but looking at how the test came out I think you can take down to less than that. I'd bet a 100-120 surface cone would still hold detail pretty well.
Attached Images
  
lisa is offline   Reply With Quote
Old 15th October 2007, 11:49 AM   #6
ggunners
Junior Member
Junior member
 
Join Date: Oct 2007
Location: Chantilly, VA
Posts: 7
Default Re: How to texture map a cone shape

Thanks! I'll give the disk method with divide loop a try.

....later the same day.... I tried the method you describe with mixed results. The [surface] [divide] function does not produce concentric circles and I did not find a [divide loop] menu item in AC3D. I can create a sphere and then flatten it, then apply the UV map texture and proceed with extending and rotating each subsequent circle.

With this method, I have good results with about 60 surfaces.

-- ggunners
Attached Images
 

Last edited by ggunners; 15th October 2007 at 12:40 PM.
ggunners is offline   Reply With Quote
Old 16th October 2007, 04:28 PM   #7
lisa
Senior Member
Professional user
 
lisa's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 917
Default Re: How to texture map a cone shape

Ooops. Shoulda mentioned, divide loop is one that needs downloaded from supercoldmilk.com.

Looks pretty good to me! Depending on how far you are from the plane, I think it's plenty smooth enough to get away with.
lisa is offline   Reply With Quote
Old 16th October 2007, 06:41 PM   #8
ggunners
Junior Member
Junior member
 
Join Date: Oct 2007
Location: Chantilly, VA
Posts: 7
Default Re: How to texture map a cone shape

Yeah, it'll work, this is about the closest it will be in the ClearView RC flight sim.

I'll grab the plug-in and see if it makes it any easier.

-- ggunners
Attached Thumbnails
Click image for larger version

Name:	extra300s.jpg
Views:	356
Size:	52.2 KB
ID:	524  

ggunners is offline   Reply With Quote
Old 16th October 2007, 06:57 PM   #9
lisa
Senior Member
Professional user
 
lisa's Avatar
 
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 917
Default Re: How to texture map a cone shape

Nice looking plane, ggunners!
lisa is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -4. The time now is 08:17 AM.


AC3D Forum
(C) Inivis Limited 2020