James_Hastings-Trew@tptbbs.UUCP (James Hastings-Trew) (06/19/91)
I don't know if anybody else has noticed this, but there is a bug in Imagine's altitude mapping. To see this bug for yourself, do the following: 1> make a simple altitude map with DPAINT. A white screen with some smooth-side dark pits would be appropriate. Make the pits big and simple. 2> in Imagine put this simple altitude map on a plane. Use your own discretion as to how to map the image, but keep it simple - flat x, flat z, with a Y depth of about 5 or so. 3> set up the plane and another simple object (like a sphere) in the stage editor, and light the whole thing from the side (does not matter which) 4> Render the picture. If you placed the light on the right-hand side, what you will see is the sphere being lit from the right, but the pits in the plane will look like they are being lit from the left. If you move the light over to the opposite side, the apparent highlights on the pits will again move BACKWARDS to where they should be. Thanks to Jeff Petkau for pointing this bug out to me. Normally when I do a bump-map it is so complex that I do not notice where the highlights and shading fall. On simple maps they become far too obvious. The bug is that the highlights are rendered mirror-image fashion on the X-axis (as Jeff said to me, it looks like somebody got a sign backwards in a calculation somewhere). If you only light your scene from above, the bumps look natural (i.e. not upside down). Would somebody out there in modem land check out this bug, and if it proves to happen on your machines (and I am certain it will) could you report it to Impulse? I don't want to report it all by myself, as they have a tendancy to disregard bug reports they get from single individuals. If we all speak up then they will look into it.