View Full Version : emit light in hdri
09 September 2006, 04:13 PM
is there an 'emit light' in hdri as in maya. emit light sort of casts light from an hdri so you don't have to light the scene manually with physical lights... which i had always thought was the big advantage of hdri. im compositing some 3d into a backplate with a matching hdri. all the tutorials ive seen use the technique of setting up the hdri, then lighting it to get the shadows.
09 September 2006, 04:42 PM
You can automatically create a light rig from your hdr with get/primitive/light/light rig from image. Depending on the settings you use, it'll create a bunch of inifinite lights according to the texture you use. If you simply want to cast a shadow, you can keep the light with the highest intensity.
09 September 2006, 04:55 PM
yes, thats been my best bet so far... im really looking for an exact match of the shadows from the hdri. for example if i have an outdoor scene with harsh shadows i want the same harsh shadows calculated from the hdri... will the light rig provide that? or will it give me a light rig of the same diffused look im getting from just the hdri/final gather?
09 September 2006, 06:56 PM
There's no automatic way to get perfectly matching shadows. Your best best is to do the light rig thing, delete all but the most intense light (or all but the shadow casting lights which you will have to determine yourself), than you probably want to change those lights to area lights and play around with the size, quality, intensity, shadow color and pnenumbra. Then, of course, you would mix the HDRI lighting back in with the shadow casting lights. You would probably want to keep the shadow pass seperate from the HDRI pass as well.
hope that helps
09 September 2006, 11:27 PM
you can also use the Ctrl_light shader that generate a geometry area light.
You can map you HDR image to drive the light intensity and the color.
09 September 2006, 03:49 PM
but i though that using HDRI maps was for "iluminating" and reflection....so does softimage just use hdri maps for reflection and NOT ilumination??:sad:...can someone answer this please.
I though that when you assign a hdri map to an enviroment shader you can control the amount of LIGHT that the hdri emint bu adjusting the "image" in the enviroment settings...?!
09 September 2006, 04:47 PM
Of course you can light scenes with hrd environments and final gathering, the "get light rig from image" tool is another way to do it which lets you create actual lights instead of using final gathering. You can use both in the same scene if you want your final gathering lighting and the exact shadows lights produce.
09 September 2006, 12:52 PM
Create HDR environment lighting and at the least, one source of illuminaton, then just switch off Light Contribution - Specular and Diffuse, now your scene will be illuminated from HDR only :beer:
09 September 2006, 12:52 PM
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