I was wrong about a possible byteswap error on 16-bit elev exports to
BMP/TGA... turns out the byteorder was correct. There might be a problem
with TGA normal images at 16-bit, but it just so happens that Leveller
never outputs such pictures (it uses 24 bit for picture exports).
However, the TGA 16-bit elev export didn't take the pixel's attribute
bit into account, so it was a little off. I've adjusted it to do a
15-bit export and leave the attribute bit to zero and now it's coming up
matched equal to the BMP export. The error wouldn't mangle anything --
it would just cause a loss of one bit of precision -- so if you're
getting weirder results, then it remains a mystery. If you have some
elevdata BMP/TGA/PNGs you can send in along with the source TER, I can
examine them.
Ray
What formats (exactly)are the 16 and 24 bit output bitmaps using?
It depends on the file format. 16-bit PNG will use 16-bit grayscale. 16-bit TGA/BMP will use a 15-bit 5-5-5 RGB encoding, and 24-bit will use a red * 65536 + green * 256 + blue encoding.
24-bit pixels are written in BGR order.
16-bit BMP/TGA may be wrong; they are writing without the pixels byteswapped. I'll have to look into this and verify.
Thanks, Ray
By that I mean how is a pixel’s height calculated?
I’m outputting to Maya which apparently only understands gray scale – odd things happen when using 16 of 24 bit. However, using the power of Maya’s Node concept, I can easily calculate my own pixel heights.
I need more than 8 bit as this is Valles Marinaris, which has a lot of steep hillsides and flat rolling dunes in it – with 8 bit resolution there are artifacts.
I’ve done some samples and the ‘native’ Maya appears to sum up all 3 RGB values to calculate the height. I imported a bitmap with a red, green, and blue ramp and it looks like Leveller uses the R as a MSB, which would give more dynamic range (i.e. the height is a 24 bit value using RGB as the 3 byte values).
If this were the case I should use R*65536+G*256+B but that seems to give weird results.
So how should I build my Maya nodes to properly calculate a 24 bit, bitmap export height based on the R,G, and B values?
== John ==
