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Subject: Cool Shadow Trick for Reduced Rendering Time


clyde236 ( ) posted Thu, 29 August 2002 at 1:20 AM · edited Thu, 28 November 2024 at 4:36 AM

Hi All, I love Bryce, but of course, like any 3-D program, as soon as I add shadows, the rendering time jumps way up. I think I found a cool trick to help get around this which can work for some scenes. (Not all, obviously). The trick is to use a spotlight on the object that is to cast a shadow, and set it to a NEGATIVE value, so it casts a black light. You have to put a lot of softness on the edges, and make sure that shadows are turned off. Place the spot so it is pointing at where the shadow would be, raise it quite a bit off the object, but have it point to the object's base (so you get a elongated cone.) I discovered this trick while making a lit candle in Bryce using Amorphium Pro objects (because they can organically make a melting candle) as .obj files. In my sample case, I had several objects in the scene. A plane object for a base surface (I used a checkerboard material), the candle base (which I put a gold material on), the candle object, the wick object and a flame object (made in Bryce). Then I added three lights. The first light was a spherical light centered on the candle flame object. Shadows turned off, but surface light visible (for the glow). The second light was a spot pointing at the candle body. Soft edges, no shadow. Low level (it is just to make the candle body more visible) The third light was a spot light turned NEGATIVE, placed behind the candle (opposite the other spot), angled as indicated above. No Shadows I turned off atmosphere and used a black color for the environment and I also turned off the sunlight and sunlight shadows. (no ambient lighting, in otherwords.) The result was a nicely lit candle that rnedered at 640 X 480 in 7 seconds! When I used the lights as I would normally try them (with shadows,) the same render took 5 minutes! I can place a turorial on this trick on my Web site. Do you think anyone might find this interesting? It won't work in all situations, of course, but in dark, moody scenes, like a simple candle in a dark room, it seemed to work. Oh, and Amorphium Pro is a really good program, and it is very cheap ($89 through some vendors, $119 on the Electric Image Web site--http://www.electricimage.com.) It has a lot of powerful features for organic modeling, supports import and export of .obj and .dxf files and does a whole lot of tricks. The only really major problem is that the manual is very skimpy for such a powerful and complex program. BUT, they have a training CD set (from Lynda.com) which really explains everything very nicely. In fact, that CD explains things about materials (specularity, ambience, refraction, etc.) and lighting that really explained these things to me much better than I had understood them from the Bryce manual. They have a bundle called the Training Bundle which comes with a Shamms Mortier book on Amorphium Pro as well as the program and the Lynda.com CD for $149 from Electric Image. I was very surprised at this amazing program, and it does a nice integration with Bryce. You can download a free trial version (Windows and Mac) that runs for 24 hours. It has the manual as a PDF, so you can fuss with it to get a feel for the thing. As to rendering? Bryce beats it out hands down every time! Electric Image claims that the render engine in Amorphium Pro is very fast, and I'm sure it is. Bryce is simply faster, at least in my limited experience so far. And there are a number of factors that could influence this experience (mostly lighting). You might want to check the program out. I was surprised at how much they packed into it for the price, and the Lynda.com training CD is really excellent. Just thought you'd like to know.


EricofSD ( ) posted Thu, 29 August 2002 at 4:12 AM

We should be doing more work with negative lights. I have to admit, I haven't done anything with them yet, so this is a good trick. As for AMPro, I bought the 3dtoolkit for a few bucks more and am very happy with it. Well worth the money. I asked in the community forum if anyone was interested in a EIU forum. It got some response, but not enough I think.


tuttle ( ) posted Thu, 29 August 2002 at 7:28 AM

I've only use negative lights once, to dim the corners of a room. Problem is, they reflect darkness on other objects, and it can look weird. But as you say, they are OK for simple scenes. I find a huge slowdown occurs on soft lights. My last pic rendered in about 20hrs, with one soft light out of 35. Originally, I had 4 soft lights, but it was taking 5 minutes for each line of pixels on the first pass (about 10X as long!). It's actually quicker to use, say, 20 normal lights grouped close together, than one soft light. I hope they make it a bit speedier in Bryce6, 'cos soft lights really do look cool.


shadowdragonlord ( ) posted Thu, 29 August 2002 at 8:41 PM

Aye, it's always awesome to optimize and try and quicken up our render times, but I think that patience is more than a virtue! I've been playing with some weird shadow effects as well, using lights with white shadows to produce a weird haze around everthing (I'll try and post the pic tonight). But to be honest, what has saved me from ever whining about render times is one thing : Sleep! Never sacrifice quality over quantity, just click the button and go pass out for a while... Actualy, I'm lying. Bryce Lightning and a small horde of Athlon-based machines have given me new faith in Bryce 5's rendering power. One more thing, I'm interested in seeing your results, Clyde, do you think you could post your candle image for me/us?


clyde236 ( ) posted Thu, 29 August 2002 at 11:35 PM

Hi All, Well, I know that a verbal description of a process is almost completely useless, so I am writing a "tute" on how I got this trick to work, which I will post soon (give me a few days, okay?) on my Web site. I made my first experiment with Amorphium objects, and that went really fast for me. Then I thought, I might like to try with Bryce objects. Well, making a realistic candle in Bryce is something of a challenge (one I didn't quite master!) but it is good enough for the lighting purposes. Used a lot of objects, including a terrain object for dripping wax, lots of negative booleans and so on. So that upped the render time a little, but with my Bryce only image (made entirely in Bryce), a render at the "default" screen only takes 16 seconds (on a MAC G3 clone-- including anti-alaising normal). This is using Bryce 5. It's been so long since I used Bryce 4 that I don;t remember if it has the same lighting control (which is the big issue here). Anyway, I am writing a "tute" on this and how to make the objects (in case it will help some folks, and won't make folks who don't have Amorphium Pro feel bad or left out). I'll post images from both renders and instructions. It will take a day or two to write it all up. Again, this technique is really only good for dark and mysterious type scenes, but you all might find other uses, or at least get your interest sparked! Stay tuned! I'll post a note here when it is ready. (Why is Bryce so much fun to play with? It's really addictive for me, I just love it, in spite of some frustrations. Do you all find it so?)


electroglyph ( ) posted Fri, 30 August 2002 at 6:37 PM

I have a spidey in london picture in my gallery. I wanted to light him from below like spotlights but it made my clock glaring white. I finally used two very dark grey spots on the clock with a white on spiderman. These smoothed the rough edges generated on my background by the white but still managed to illuminate the scene's shadows. Spiderman also came out with too little light for my taste. What your saying is I can use a spot to "remove" light from a scene? That would have worked so much better! I will try it on the file tonight. I'd also like to see the tuit when you are done. Thanks!


shadowdragonlord ( ) posted Fri, 30 August 2002 at 7:13 PM

Aye, electroglyph, negative lights have been around since Bryce 3D I believe, and they are an awesome tool! Imagine if you could make a spot-dark, or a flash-dark! Nobody does that in real life...! What if they (read : God?) made negative suns! Or negative wind for example? What would negative wind feel like? I need some sleep...


electroglyph ( ) posted Fri, 30 August 2002 at 9:21 PM

Negative suns! aren't those black holes? Light checks in but it doesn't check out. Negative wind on the other hand, that would probably suck. Just sign me, Past the point of needing some sleep. + } +


clyde236 ( ) posted Sat, 31 August 2002 at 12:49 AM

I believe we already have negative wind, it's called a vacuum cleaner! And an interesting history on the development of negative wind comes from the world of music. European reed organs (i.e. the Harmonium) used wind under pressure (i.e. compressed air) to blow the reeds. This was developed from the pipe organ at the end of the 18th century. The idea of a reed organ actually came from China, an instrument called the "Sheng", made of bamboo. Anyway, in America, the sound of the Harmonium didn't catch on, as it was considered too harsh. It produces the full range of harmonics which are very harsh sounding. Very few instruments can do this as effectively or with as much force. American innovators got the idea of reversing the wind (negative wind) and pulling it INTO the instrument! The case of the instrument made enough of a sound barrier that the harsh harmonics (which have very little sonic energy) were absorbed. The result was the American Reed Organ, which many of you may know as the "Pump Organ" or the "Parlor Organ". It caught on like gangbusters in the 19th century (especially out west because the instruments traveled well and rarely needed tuning) and well into the 20th Century. Hundreds of thousands of the instruments were made and sold. It was as popular for its time as the many electronic keyboards we see today. Not many people today care much for the sound of reed organs, however. A relative of that instrument is one we still can buy today, called the Harmonica, or "mouth organ". And then there's the Accordian family. As anyone who has ever played one knows, these instruments sound under both pressure and suction. Again, the sound is something of an aquired taste. But not only that, the idea of negative wind made player pianos possible because they could use a paper roll with holes in it (very similar to modern MIDI music software that uses a graphic editor) to make the insturment play. Prior to that, huge and heavy cardboard "books" were used, and only in fairground organs (i.e. the carosel) The bar against which the paper rides (called the "tracker bar") has many holes (one for each key on the piano, plus some control holes) and uses negative wind. This suction holds the paper tight against the bar. When a hole in the paper lines up with a hole in the tracker bar, it causes a little bellows in the piano to collapse, throwing the hammer against the string. They actually tried this design with wind under pressure (positive wind), but of course, it blew the paper away from the tracker bar and didn't work! So, even though "negative wind" sounds like a joke, it actually exists, and we use it all the time! As to negative suns...black holes seems about right based on the description. Just thought you'd like to know.


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