Rendermap is an effect which allows many different types of effects to be created from converting textures to different types of projections all the way to orthographic rendering with custom lenses.
The basic process of rendermap is that you apply a texture to a surface to define the canvas. Rendermap then creates a virtual camera and takes pictures of each pixel of the canvas (including other textures/lighting/effects that exist in the same place). The camera interest is placed on the surface at the location of the pixel while the camera is lifted to a microscopic amount off the surface in the direction of the surface normal. The camera will continue along the surface stopping at each pixel within the canvas and record the results. For this reason, each of the canvas's pixels can only appear in one place on the surface - otherwise rendermap will be confused as to which value to use for the result.....or you'd end up with a result you'd rather not have.
This flexible setup is what allows the many effects to be created. The canvas can be made transparent so it doesn't interfere with other effects residing in the same area. Also, by making the canvas transparent, you can capture what's inside/on the other side of the object. This is useful for capturing custom orthographic views, making panoramas, or even making lightmaps for radiosity calculations.
A couple of Possible rendermap setups (more exist than listed):
Method #1: Hidden duplicates. Useful when the target object has complex texture assignments and many materials.
1) Select target object and duplicate it.
2) On the duplicate, apply a 2D local texture where you want to receive the rendermap effect. It's best to use UV mapped images. You can strip the surface of it's previous materials/textures if you wish.
3) Hide the duplicate.
4) Open the schematic view and activate "matter" mode from the dropdown menu.
5) Matter > Txt_Oper > Rendermap+.
6) Click the texture node on the duplicate object.
7) In the popup rendermap dialog, use default settings to begin with. click OK.
When the effect completes, you'll see the perspective view jump for a split second and the Txt_Oper menu cell turn off.
Method #2: Hidden Textures. For simpler setups.
1) Select target object and Matter > Texture > 2D Local.
2) Click "next" and apply a picture of your choice.
3) Set "blending" to zero on the right side of the texture editor. click OK.
4) Open schematic view and make sure object and it's texture nodes are visible.
5) Matter > Txt_Oper > Rendermap+. click the texture node of the hidden texture.
6) Use default settings for the rendermap effect for now.
When the effect completes, open the texture editor and reset blending of the rendermapped texture to 1 to see the results.
Method #3: Panoramas (aka custom lens)
1) Get > Primitive > Circle (NURBS or BSpline). Accept with default settings.
2) Rotate 90 degrees on X.
3) Model > Effect > Freeze > Rotation/Orientation.
4) Extrude the circle in Positive Y to create a cylinder.
5) Model > Effect > Inverse. This will put the surface normals facing inwards.
6) Matter > Texture > 2D Local. Apply an image of your choice. Set blending to 0. click OK.
7) Matter > Material. Make material 100% transparent. Click OK.
8) Make sure schematic view displays object and it's texture(s).
9) Matter > Txt_Oper > Rendermap+. click the texture and accept rendermap defaults. Click OK.
10) When rendermap is done, open texture editor and reset blending to 1 to see the results.
Change the shape of the cylinder, or even unwrap it to create your own custom lens for capturing orthographic views (if it's a grid), fisheyes (parabolic discs), or other custom effects if you perturb the normals (polygon objects).
Method #4: converting 3D textures to 2D (or change 2D projection type)
1) Select an object and apply a 3D texture (local or global).
2) Matter > Texture > 2D Local. Apply a texture then, you guesed it, set blending to 0. click OK.
3) Open schematic and make sure texture nodes are visible.
4) Matter > Txt_Oper > Rendermap. Click the texture node and accept with default settings.
5) Matter > Texture > 2D Local. Reset blending to 1 to see the results.
Notes:
1) textures used for receiving the rendermap effect MUST be applied as a 2D Local texture.
2) Each pixel from a texture to receive the effect can only appear in one place on the target surface. Most projections do not conform to this as they project through the entire object.
3) If rendermapping a surface (NURBS or Bspline), boost the step counts before applying the effect to reduce artifacts from shading or tessellation.
4) If you do not wish to capture lighting in the result (such as when transferring a projection to a UV map), then convert the underlying materials to constant before applying rendermap.
Hope this helps,
Matt
Matt Lind
Animator / Technical Director
Softimage certified instructor:
Softimage|3D
Softimage|XSI
speye_21@hotmail.com