LightWave 3D 8 Lighting Wordware game and graphics library phần 9 pot

Cache Radiosity would be a vastly more useful tool if the cached radiosity solution, instead of being held in local memory, were held in a file. That way, networked machines could access the information the same way networked machines access Particle FX solutions from a sin - gle file for particle renders. I’m sure if enough of us continue to make noise about this, NewTek will see fit to include it in the next great release of LightWave. Faking Soft Shadows No doubt about it, sometimes we just can’t use radiosity to achieve those beautiful soft shadows we have come to know and love. The truth is, it is very difficult to fake that kind of quality, but there are many situa - tions in which that level of quality is not necessary because there may be heavy motion blur in the shot or perhaps any soft shadows are not forefront in frame. If you come across a situation where the soft shadows are unimportant enough to fake, you should do it. There are literally doz- ens of way to fake soft shadows. Here are a couple of my favorite tricks. They’re easy, quick, and provide reasonable results without major ren- der power. Using an Area Light OK, using an area light isn’t exactly what we’d call a quick render, but it’s quicker than radiosity in most cases. The first rule with area lights is to keep them as small as possible. The larger the area light, the more render time is required. Second, try to reduce Area Light Quality to 3 instead of the default 4. I have never been able to get away with less than 3 for a final render, although I have never had to go above 4 either. The maximum quality for area lights is 5. Getting a soft shadow out of an area light is easy. Place it, turn up the intensity, and render. The larger the area light, the softer your shad - ows will be. Chapter 25 ······································ 412 Using Spotlights and Shadow Maps This is a favorite of mine because spotlights with shadow maps render very quickly and because spotlights with shadow-mapped shadows are the only light in LightWave other than area lights that provide a built-in soft shadow. These are also extremely easy to set up and, although the quality of the shadows is not nearly as good as area lights, it’s a reason - able fake that’s good enough to make it on the big screen. Let’s look at our mechanical bug scene and open up the Light Prop - erties panel where we will change our area light into a spotlight. We’ll turn on shadow-mapped shadows, select a nice high map resolution like 2000, and set the map fuzziness (blur) to 15 for a nice soft edge. ··································· Tips, Tricks ’n’ Tutes 413 Figure 25.119 Figure 25.118 Make sure you place the spotlight where it will illuminate your whole object. I like to do this by using the Light View. Or, if you need the light to illuminate other things in your scene but only need the shadow for your object, make Shadow Map Angle smaller than the cone angle of your light, and make sure the object is contained within the square representing the shadow map angle. Now render it out and take a look at those soft shad- ows. Compare them with the shadows from the area light. As you make your shadow softer, you will start to notice that the shadow stands away from the object casting it, giv - ing the impression that the object is floating above the surface. This is a nor - mal side effect of very fuzzy shadow maps. Since the “softness” of the shadow is nothing more than an edge blur, the shadows will blur evenly all around the edge, even where it is directly under the object. This sometimes makes it appear that the shadow is not contacting the object. Chapter 25 ······································ 414 Figure 25.120 Figure 25.121 Figure 25.122 If this is a problem, simply decrease the fuzziness setting or select a dif - ferent method of creating soft shadows. Using the “Spinning Light” Trick This lighting trick is an “oldie but a goodie.” The spinning light trick has been attributed to many artists over the years, but it is generally accepted that this technique was first implemented in LightWave by Dave Jerrard, one of the original LightWave gurus — He Who Has Been Around A While — although it may have been independently discovered by other artists as well. Dave came up with it back in the mists of time when LightWave 3 was released. It’s a very clever concept. Once you figure out how it works you will probably scratch your head and wonder how the dickens it was conceived in the first place. It is a good trick for creating fairly accurate soft shadows in LightWave. Before area lights existed in LightWave, the spinning light trick was the only way of creating fairly accurate soft shadows in LightWave, since all the other light types are cheap approximations of real-world lights. Its whole premise is based on how LightWave calcu- lates motion blur, so let’s take a look at that first. LightWave calculates motion blur by interpolating motion from the previous frame to the current frame multiplied by the Blur Length set- ting in the Camera Properties panel. For example, if you have low antialiasing on, LightWave will render the frame five times. For each of the five render passes, any objects in motion will be moved one-fifth of the Blur Length percentage further along in position from where the objects were in the previous frame to where they are in the current frame. All five render passes are then sandwiched together and the edges appear as though they are blurred. If the motion is high enough, you can actually see the stepped edges of each render pass. ··································· Tips, Tricks ’n’ Tutes 415 Figure 25.123 If the motion is high enough to make the stepping visible, then you have the option of setting your antialiasing to a higher level, in which case, LightWave will calculate more passes to make the steps closer together, hopefully fooling your eye into believing that it is real motion blur. Naturally, since a moving object is motion blurred, and therefore has stepped antialiasing passes, its shadows must also be motion blurred and have stepped antialiasing passes. This is where we get into the territory of the spinning light trick. The second thing we have to understand is how soft shadows work. We understand that even the softest shadows are hardest near the object casting them and softest farthest away. So if we have a whole bunch of lights pointing inward toward an object, we will get this soft shadow effect. That is, after all, essentially what the sky is — a huge array of lights all pointing inward toward the object. The spinning light trick puts these concepts together. Start by opening up a fresh Layout and loading in a ground plane and some object to cast shadows onto the plane. I’ll stick with my metal bug. In my scene, I position the default distant light over the object so you can see it. In reality, the position of a distant light is irrelevant since its rays are all parallel. Only the direction of the light will make any difference. Now clone the distant light five times, and rotate four of them so that the rotations are evenly spaced. We end up with an array of distant lights all in one spot, all facing different directions. Since the position of distant lights is irrele - vant, we can argue that this is just the same as placing a bunch of lights all around the perimeter of our scene pointing inward. Let’s render a frame and take a look at the shadows. Don’t forget that since we now have five lights, we’ll need to reduce the intensity on all the lights; otherwise our scene will probably be overilluminated. LightWave light intensities are additive. Chapter 25 ······································ 416 Figure 25.124 See the shadow array created below the object? There are five distinct shadows. Now let’s remove the four extra lights we added. Instead, we’ll spin the one distant light with an Antialiasing setting of Enhanced Low. Don’t forget to turn the light’s intensity back up to 100% for this test. Open your Camera Properties panel to set the antialiasing level. Make sure Motion Blur is set to Normal and Blur Length is set to 50% as well. Now, set a keyframe for the distant light at frame 0. Set a second keyframe for the light at frame 1. With the distant light selected, open the Graph Editor and make the light’s heading 0 degrees at frame 0 and 720 degrees at frame 1. Set Post Behavior to Repeat. We mak e the light rotate 720 degrees, or two full rotations, on each frame because the motion blur is set to 50%. 50% of 720 degrees is 360 degrees. This means that for every frame, the distant light will rotate exactly once. If we set the antialiasing level to Low or Enhanced Low, then we expect there to be five distinct shad - ows beneath the object, just as there were when we had the five separate lights. ··································· Tips, Tricks ’n’ Tutes 417 Figure 25.125 Figure 25.126 Let’s have a render and see. That’s fairly similar to the render with five lights. Now let’s try to smooth those shadows together a bit. We’ll increase the antialiasing level to Enhanced Medium, which will give us nine passes. In addition, we’ll turn on Dithered Motion Blur instead of Normal. That change will double our number of passes. The goal is to try to make the “stepping” invisible and blurred or unnoticeable to the casual viewer. Now we could continue to smooth out the shadow by increasing the antialiasing level, but each level higher we go doubles the render time. So we can add more lights instead. Clone the dis - tant light twice and parent both clones to the original light, but remove the motion keys from the clones. Rotate the first clone on its heading by 120 degrees, and rotate the second clone –120 Chapter 25 ······································ 418 Figure 25.127 Figure 25.128 Figure 25.129 degrees. Now the three lights’ rotations should be evenly spaced. Run a test render. Adding the two extra lights will add a little time as LightWave now has to calculate ray tracing for three lights, but you get triple the number of shadows for just a little more render time. Obviously, you can fur - ther improve the shadow softness by increasing either the number of lights or the number of antialiasing passes. Remember, though, as you add more lights, you need to proportionately reduce the intensity level of all the lights. Note: There are many variations on the spinning light trick. For instance, you can “wiggle” a light’s heading a bit between two frames and then repeat the motion. We often use this for cheap soft edges. Another good one is to offset a light from a null a bit, target it to an object or another null, then spin the first null 360 degrees and repeat. This way you get a focused light at the target point and increased softness out from there. You have the spinning light, the moving light, the wiggling light, and a million other vari - ations to soften hard shadows. Faking Volumetrics Volumetric lighting is that light you see in a smoky room. It’s the rays of light shining out of the trees and through the fog, the “God” rays coming from those silver-lined clouds. In other words, volumetric lighting is simply light rays that are illuminating particulate matter in the air. This fake volumetrics technique is the last trick in this chapter. It’s another technique belonging in the “old but good” category as it is sim - ple to set up and use and can save you major render time. This trick was also developed way back in the early days before LightWave was equipped with “real” volumetrics. ··································· Tips, Tricks ’n’ Tutes 419 Figure 25.130 The Old Geometry Trick One thing we know about volumetric lighting is that if you don’t actually have to have the camera fly through it, it doesn’t have to be an actual volume. This is one of the easiest and most obvious tricks in the LightWave arsenal. If you need a volumetric spotlight, just create a cone in Modeler, stick it in front of the light, and add some illumination and a nice transparency falloff to the cone. I’ll use a gradient based on a weight map. So let’s open up Modeler and make the cone. Now select the point at the top of the cone and create a weight map named Volumetric. Chapter 25 ······································ 420 Figure 25.131 Save the object and send it to a fresh, default Layout. Once in Layout, change the default distant light to a spotlight, then parent the cone to the light. You may need to rotate the cone so that it aligns with the light’s beam. Open the Surface Editor and select the cone’s surface. Open up the Luminosity Texture Editor. Set Layer Type to Gradient and proceed to set up the values shown in Figure 25.134. ··································· Tips, Tricks ’n’ Tutes 421 Figure 25.132 Figure 25.133 [...]... properties of the lighting tools to demonstrate a number of different techniques for dealing with each lighting scenario The purpose of this is to demonstrate the flexibility of LightWave s lighting toolkit and to put into practice the lighting theory and tool descriptions found earlier in the book I hope you find these short tutorials useful in describing the many uses of LightWave s lighting tools Exterior... light and other lighting effects to obscure the shadows When you are doing a cloudy day, that’s all there is to look at so your shadows better be nice and soft with no stepping Spotlight Probably the cheapest way to accomplish this is by using a simple spotlight with Shadow Map enabled instead of ray tracing and with a high Shadow Fuzziness setting Start with a fresh Layout and add a ground plane and. .. tutorial, select your sky fill distant light and open the Light Properties panel Switch Light Type from Distant Light to Spotlight Then click on the Shadows sub-tab and switch Shadow Type to Shadow Map Make Shadow Map Size 1000 and set Shadow Fuzziness to 5 Now in Layout, switch to Light View and make sure the light is lining up with the object and completely covering it and any other areas around it you may... fine-looking soft shadow for a fuzzy spotlight, if I do say so myself Figure 26.15 Distant Key, Area Fill Moving on, we keep our distant light as our sunlight key and get into some of the more render-intensive options for a fill light As our lighting and shadows become more mission-critical, and as we have less motion blur and other artifacts to hide our cheats and tricks, we sometimes find ourselves... Then load up some object and a ground plane onto which we can cast shadows Open the Light Properties panel and switch Light Type from Distant Light to Spotlight Click on the Shadows sub-tab and change Shadow Type to Shadow Map Add a new spotlight to the scene Place it directly above your object and pointing straight downward Turn on Shadow Map, set Shadow Map Size to 2000, and set Shadow Fuzziness... a premium Spot Key, GI Fill I’ve said it before and I’ll say it again: There is nothing quite as beautiful and accurate as LightWave s global illumination So scrap the sky fill light by opening its Light Properties panel and turning the intensity down to 0% Or you could just delete the light from the scene if you like Now open your Effects panel and click on Gradient Backdrop to enable LightWave s... techniques at all It is to provide you, the reader, with Figure 26. 39 practical understanding and experience of some of the myriad uses and combinations of LightWave s lighting tools You may end up using actual techniques from this section I know I do all the time But that’s not the purpose Before we carry on with a completely new lighting scenario, let’s take a look at a similar one Exterior Cloudy... Sunny Day This is a very common lighting scenario and a very good place to start since the lighting setup is very simple If you find yourself in a situation where you must create a lighting setup for an exterior sunny, clear day, the first thing you should do is examine that environment and decide exactly how many light sources exist and what their position, angle, color, and size are Typically, exterior... this setup Open your Light Properties panel and click on Global Illumination to open that panel Select Shading Noise Reduction and Enable Radiosity Then change the radiosity type to Backdrop Only That’s it Now render out a test frame by hitting the F9 key Figure 26. 28 Figure 26. 29 Using GI as a skylight fill source takes considerably longer to render than spotlights, distant lights, or area lights,... tutorials have been designed to help you understand how to implement specific tricks and techniques, rather than teaching particular lighting setups or techniques For tutorial examples of a few of the infinitely variable lighting setups, please see the following chapter 424 Chapter 26 Lighting Setup Examples For those of you who prefer concrete examples of lighting setups, this chapter contains a number . easiest and most obvious tricks in the LightWave arsenal. If you need a volumetric spotlight, just create a cone in Modeler, stick it in front of the light, and add some illumination and a nice. lighting tools to demonstrate a number of different techniques for dealing with each lighting scenario. The purpose of this is to demonstrate the flexibility of LightWave s lighting toolkit and. Maps This is a favorite of mine because spotlights with shadow maps render very quickly and because spotlights with shadow-mapped shadows are the only light in LightWave other than area lights that