[Radiance-general] Re: Modulating diffuse albedo by an image

[Gregory J. Ward]

Hi Claus,

Assuming you are using "picture.cal" for your coordinate mapping, you
can take advantage of the "inpic" variable to create a mixture
between your colorpict and a constant value, e.g.:

void colorfunc constRed
4 0.8 0.02 0.02 .
0
0

void colorpict myPic
7 red green blue myPic.hdr picture.cal pic_u pic_v
0
1 0.667

void mixfunc myMix
4 myPic constRed inpic picture.cal
0
1 0.667

myMix plastic myMat
0
0
5 1 1 1 0 0

etc...

Naturally, you'll want to apply the same transformations to both
colorpict and mixfunc if you have any, and the 0.667 value I've
specified for the picture aspect ratio should be adjusted to match
your source image (height/width).  I hope this is clear enough.

Best,
-Greg


> From: "Claus B. Madsen" <cbm at cvmt.aau.dk>
> Date: December 13, 2007 5:28:41 AM PST
>
> Dear List members,
>
> I have written a function file which allows me to project real images
> taken with a calibrated camera onto the (manually) modelled
> geometry of
> the scene (see attached images). Writing the function file was dead
> simple thanks to the really powerfull and well-designed function file
> framework.
>
> I have used colorpict to modify a plastic material with parameters
> (1 1
> 1 0 0), i.e. a perfect diffuse reflector. My function file tells
> colorpict what uv coordinates to use for a given ray.
>
> My question/problem is: how to handle the ray intersection points that
> do not map to a pixel in the back projected image (i.e., points
> that are
> outside the field-of-view of the original image). The attached image
> clearly shows how the top and bottom image lines, and left and right
> image columns get smeared across the geometry because I am
> computing uv
> coordinates which in fact are outside the image bounds.
>
> What I really want is to be able to return a controlled (constant) RGB
> value for all uv coords falling outside the image bounds.
>
> Suggestions, anyone?
>
> Best,
> Claus
>