Light sources, populations and png images

Started by Granknight, August 26, 2010, 04:41:33 pm

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Granknight

August 26, 2010, 04:41:33 pm Last Edit: August 26, 2010, 04:43:51 pm by Granknight
I'd have a few questions about tgd i haven't found in the forums...
Is it possible to make a light source population? i mean, populating light sources instead of objects?
Is it possible to give more rotation angles to population? example: something like, 88°-92° , 118°-122 and 278°-282° in a single population.
Would it be possible to populate something raindrops in a storm? I am aware that it's possible to populate things in the air using planes, but is it possible to populate in 3 dimensions?
Is there a way to have a blurred FOV effect without doing it in postprocessing (this effect could be found in a terragen 0.9 plugin)?
Is there a way to use png images on planes, mantaining the opacity from png? For example, placing a plane with an image map of a person in .png (with transparency where the background would be in the image) and being able to "see" across where the transparency would be?
Thanks for your time and attention ;)

edit: sorry, i choose the wrong board... can one of the mods move my topic please?

Oshyan

You can not populate light sources at this time, but you can make luminous objects and populate those. Use very high values for luminosity (10,000, 100,000, or more - the larger the object the higher the value needed). As long as you render with Global Illumination (GI) the luminous objects will light up the surroundings. This is not as easy to deal with as light sources, but can be useful depending on your needs.

The rotation values you specify in a population are ranges. If you specify 0-360, there will be objects anywhere in that range of rotation (i.e. any rotation angle). You cannot specify multiple ranges, but you could use multiple overlapping populations with different ranges to achieve a similar effect.

You can't currently populate volumetrically, but rain would not be best handled this way anyway. You'd need a very high number of drops to create a convincing effect. Instead you can use stretched, low-density clouds for distant rain, or elongated "rain" objects in multiple planar populations close-up. A search for "rain" in the forums will find some topics discussing these techniques.

DoF ("blurred FOV effect") is not currently possible natively within TG2. We are testing development of a function to do this, but it is not yet ready for public use.

Not sure if PNG transparency is supported - you can try it with the appropriate option in the Image Map Shader: under Effects tab, Alpha As Opacity.

P.S. I also moved your topic to the right place.

- Oshyan

airflamesred

Thats interesting about the luminosity Oshyan. Hadn't realised it needed to e so high. Thanks

Oshyan

Yeah, I don't remember the details, but the luminosity is relative to the area of the object. So say you have a cube 1 meter to a side. 6 sides gives you 6 square meters of area. If your light source is 600, you have 100 "light units" for each side, theoretically. Now scale up your cube to 10 meters on a side. You now have 60 square meters of area and only 10 "light units" for each side. The light cast will be comparatively weaker because it's spread out over a larger area. So luminosity needs to be proportional to object size, basically. Keep in mind this explanation is entirely non-technical and may not be exactly correct, but hopefully it communicates the general idea.

- Oshyan

Matt

September 01, 2010, 02:37:06 am #4 Last Edit: September 01, 2010, 02:41:49 am by Matt
If you are using luminous surfaces and GI to create light, the larger your objects (or the more objects you have) the more light they will produce, since the same surface luminosity is multiplied by a larger surface area. Surface luminosity is a measure of flux per unit area of the surface - it's the actual colour of the luminous object. So if you have a very large object (or many of them), the luminosity won't need to be very large to create a lot of light.  But if your object is very small and far from the point you want to illuminate, you are better off using a light source.

I think Oshyan is confusing this with the intensity parameter on light sources, which works the other way round, because the intensity parameter is an absolute measure of the total energy emitted by the light source. The surface colour of the "visible object" portion of a light source then has to be calculated from that (since you don't get to specify the surface colour directly), and it is proportional to the intensity divided by the surface area of the light source. Yeah, it's confusing :)
Just because milk is white doesn't mean that clouds are made of milk.

airflamesred

Thank you once again chaps, I can think of some uses for this.

Granknight

sorry if I am late to reply... thanks for the help!