Rendering with Spotlights

# 1 09-11-2006 , 07:45 AM

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I just started using maya and don't understand why my rendering is not working. I am using four different spotlights to light a skewed nube sphere. I like the image that I created, but when I render it, all I see are four round white spots instead of my image. I have tried decreasing the penumbra angle and turning on and turning off the mental ray, ray tracing, depth shadows etc but nothing makes the rendering look any closer. When I make one spotlight's light encompass the entire image I want, the rendering looks fine. But I like the image in which four spotlights focus on different parts of the sphere. Do you know what I am doing wrong?

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# 2 09-11-2006 , 12:42 PM

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rosie56,
It sounds like you may not have any ambient light in your scene. If that is the case, then only places focused on by the spot-lights will be lit.

Just go to Create->Lights->Ambient_Light. Adjust brightness to taste.

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# 3 14-11-2006 , 12:20 PM

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no don't do that at all! Ambient light is a flat light that will not cast shadows and thus will flatten your image out and it will look awful. You can get the same effect by having your spotlights not casting shadows (light will pass through objects and light them evenly and flatly)

Post an image of what's coming out of the renders.

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# 4 14-11-2006 , 02:57 PM

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Oops!

Just figured since the four spots are all on the sphere that s/he doesn't want to throw shadows. I understood the intention to be that of illuminating the parts of the sphere that were not subject to the spotlights.

Still though, I don't quite understand the problem of my solution looking flat on account of it's lack of shadows. How would this be different in appearance to turning off the shadows of a spot?

I've only got back into 3d in Sept this year. The last time I was doing 3d was with 3DS R3 & R4.

With the limited power available (i.e 486 DX2 66) and the 'cutting edge' rendering technology avail at the time, it was much quicker (and easier on the HUGE 32Mb of ram) to use an ambient, on account of there being no transformation work done on the light. Nor is there any need to calculate areas affected by said light, since an ambient affects all object equally. (and practically zero calculation time)

Mind you, in retrospect, on today's machines saving a couple of thousand clock-cycles is not even worth the effort of laughing at. I mean a whole couple of thousand in some 2 or 3 thousand million. Lol...

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# 5 14-11-2006 , 03:14 PM

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ok create a cube and a plane below it.

Now place an ambient light inside of the cube. Render. You will see your whole scene is lit up and it shouldn't be right?

now create a spotlight and place it inside the cube facing down to the plane. What do you think should happen? Render. You will see that the plane is lit up where the spotlight is.

Now turn on depth map shadows on the spotlight and render. Your scene should go black. This is because you now have shadow calculations which make the light realise that it's inside a box and shouldn't illuminate the plane below.

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# 6 14-11-2006 , 04:02 PM

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:blush:
Ah hah!

I think I've nutted out this little mis-communication.

I was rather literal in my interpretation of the problem posed. I took the image to consist of the skewed sphere, and nothing else. My mistake. Sorry about that.

Thanks for your directions Allan. You've helped enlighten me (pardon the pun, if you will) on the differences between the way that Maya uses the position of the ambient light in it's lighting calcs and the way that 3DS r4 did not.

My recollection of 3ds was that an ambient light was simply defined and had a colour and intensity, but no position. When placed on one side of the cube, I'd expected to see the ground plane on the other side illuminated just as brightly as it was on the side of the light.

So too do I see what you mean about the zero-shadow spot-light having more 'depth' than an ambient. Not that I could describe it any other way...

Thank-you most kindly, Sir.
:nod:

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