CompuServe Messages

#Lenzfx

    27-Dec-94 00:26:42
Sb: #143737-#Lenzfx
Fm: Scott Roberts 75604,1712
To: Aaron W. Ostler 74672,127
Aaron, Hope I didn't seem too hostile in my last note, I'm writing under the influence of a cold. <<What you are seeing any time you perceive a surface is light rays interacting with the atomic structure of that surface.>> Yikes! I didn't think you'd get THAT detailed : ). <<Whether these light rays come directly from a light source or are reflected from another object is irrelevant. So, it is possible to have an out-of-focus object appear to be in focus in a reflection if the surface of reflection is in focus.>> I don't believe that this is entirely correct. While it is possible, as in your movie star example, it is not always that way. The focus, or non-focus, of the mirror is fairly irrelevant to the state of focus of the reflection. The image reflected doesn't gain any special properties because of the location of the mirror. The reflection's state of focus is solely dependant on a simple equation: the distance from the viewer to the mirror + the distance from the mirror to the reflected item. The reflected item's image is treated the same as if it were located at the resulting distance. Its state of focus and the effects of atmosphere are calculated the same way. <<The distance from the camera to the movie star's head is out of the focal range, but the distance from the camera to the mirror is in the focal range and you get a crystal clear reflection in the mirror while the head in the foreground is out of focus.>> This is NOT why the mirror and the reflection of her head is in focus while her head is not. As I stated in my last note, it is because the focal range begins at a distance beyond where her head is and extends to a distance beyond the distance of her head's reflected image. Why do you think that her head's reflection is the same size as it would be if it were at a distance equaling the distance to the mirror + the distance from her head to the mirror? Wasn't all this figured out 400 years ago by DaVinci et al? In your sample image the table is in focus, the wall is out of focus. The distance from the viewer to the table + the distance from the table to the wall cannot be shorter than the distance from the viewer to the wall. So the wall's depth is between that of the table top and the reflection of the wall. It isn't possible to have an out of focus object at a distance between two in-focus objects. My friend DrS has a more plausible explanation of why this effect is happening. He thinks that 3DS will not allow you to apply the depth-of-focus effect before 3DS figures reflections and then allow you to apply the depth-of-focus effect again to the surface with the reflection on it. I must admit that this is a formidable task, as you would have to make several calculations for a reflection of a reflection. This appears to be what is happening in your sample image. The reflection on the table top is treated as a texture map and your depth-of-focus effect is applied to the general scene. This may be the only option which the software allows short of raytracing. If so, then its a shame. I can't use an effect which only looks realistic if I don't have any reflections in the scene. My question is: if this is the reason that this is happening in your sample, then why not just say so? I'm not implying that you are trying to hide a flaw- maybe you just never noticed it, or maybe this sample image wasn't created correctly. It's just that your movie star in the mirror explanation got my dander up- it doesn't explain why the sample image was incorrect (which it is), it merely dances around the problem. If I'm going to spend $300 dollars on a piece of software, then it had better state what it can or can't do, or you'll get a lot worse notes than mine. Hope this wasn't too negative (or too lengthy). I was suprised by your quick and pleasant response and I hope you don't take my criticisms personally. I'm sure that you know alot more about programming for 3DS than I ever will (or want to). Some day soon (hopefully), I'll be uploading some of my current project (a pc playing basketball) and you can feel free to pick it apart at will! thanks Aaron! scott