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Shadows 5.2 Newbie Dumberer
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Shadows 5.2 Newbie Dumberer // New Users
Post by glhalleck // Jun 18, 2008, 9:44pm
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glhalleck
Total Posts: 12
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Some say; "no questions is a dumb question". I may be able to prove otherwise....here goes:
My very first project is a landscape. I feel that I am getting to the point of using this as my "basic" canvas" to start working on. This is obviously very raw..(not even an object for the light source yet). Don't laugh. I have no idea what I am doing yet....obviously.
I've tried to read as many tute's as possible....but for the life of me, I can't figure out how to cast shadows.
I've barely started to even understand what Ray Tracing or Casting is...but it seems that's not the answer. And when I "screw around" with the lighting controls, it doesn't seem to even give me a clue either. I can't even figure out what "toggle shadow casting by current light" means. It doesn't seem to do anything. Well, not the way I'm doing this anyway. But I don't have a freakin' clue!
Can anyone help this idiot? ....Please, I'm embarrassed but tryin'.
Thank you.:confused::( |
Post by splinters // Jun 18, 2008, 9:58pm
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splinters
Total Posts: 4148
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When you select a light, there is an icon to the right of the light panel which pops up that toggles the shadows on or off (icon has a shadow...or not, to show the state). I cannot remember but does version 5 have a raytracing option in the render panel? If so , make sure it is enabled.
Either or both should sort your problem out..it has been a while since I used version 5! |
Post by jamesmc // Jun 18, 2008, 10:10pm
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jamesmc
Total Posts: 2566
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On the toggle shadow light, it means that - it will cause Each light to toggle on or off it's shadow casting ability.
The first image shows toggle off.
The second image shows where the toggle shadow is turned on for an infinite light (the small white light bar on the floor)
The third image shows the effect of the toggle on for that particular infinite light. (long shadow stretched across plane)
I'll let others explain the other questions you had, don't want to mess it up. :) |
Post by TomG // Jun 19, 2008, 3:26am
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TomG
Total Posts: 3397
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One thing to note is to follow James' example, and not try working with shadows in your complex canvas. Instead, go back to a basic test scene so that there are fewer factors to interfere with learning.
For instance looks like you may have a sphere enclosing the scene to give the night sky (maybe not, but could be). If so, then you could have a shadow casting light outside the sphere and you wouldn't see its result, as the sphere would block the light altogether.
To avoid any such complexities, a simple cube for the ground, one object placed on top of it, and one light only, and there you have your test scene.
Toggle Shadow Casting For Current Light is what you need - when active, the light casts shadows, when inactive, the light casts light but no shadows.
Raytracing is the act of firing a ray from the camera position into the scene to see what objects it hits. When it hits an object, the color of the surface at that point is calculated (which may spawn another ray if the surface is reflective). The point on the surface looks to see if it is hit by light from the light sources at this point. So the renderer "traces" the path a ray takes through the scene.
Raytracing is required for things like reflection and transmission, as those require the ray to be traced from the camera, to the surface, then reflected or refracted and the new direction of the ray needs to be traced til it hits another surface, and so on.
There are two shadow types for lights, Ray and Mapped. Ray gives sharp shadows, and requires Raytracing to be enabled to have an effect. Mapped shadows give soft shadows, they calculate an image which they apply to the surface that controls the shadows, and doesn't need raytracing enabled to show up (but will also show up when Raytracing is enabled).
Mapped shadows cause a pause before the scene starts, but once it starts may be faster overall than using Raytraced shadows. The mapped shadows may use more memory, especially if you raise the settings to avoid blocky or pixellated results.
Working with a simple scene should let you adjust all the parameters for shadows, turning them on and off, changing the light type you use, adjusting the various settings for Mapped shadows, etc.
Once you have a feel for it, you can head back to your more complex scene and apply what you learned there :)
Oh, note that you can turn individual objects to have Cast Shadows and Receive Shadows off separately. With Cast Shadows unchecked, the object doesnt cast shadows even if the light does (handy for sky and star domes, so that they don't block all the light turning the whole scene into shadow). With Receive Shadows unchecked, it means that any shadows that normally would fall on an object do not get rendered. Handy for objects that are meant to be glowing or self-illuminated. For instance, a light bulb object generally would not Cast nor Receive shadows.
Again experiment in a small and simple scene and take it from there!
HTH!
Tom |
Post by jamesmc // Jun 19, 2008, 7:54am
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jamesmc
Total Posts: 2566
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Tom is smart.:cool:
It's why he should post comments about technical stuff and not me. :p |
Post by TomG // Jun 19, 2008, 9:17am
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TomG
Total Posts: 3397
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Thanks James, but you should definitely be posting comments on tech stuff :) You answered the core of the question, I just added some background that gives a bigger picture, not immediately useful but longer term might be interesting to know - but in the end you were already there with the real answer to this problem and some nice pics to illustrate besides :)
So do keep posting!
Tom |
Post by glhalleck // Jun 20, 2008, 11:36am
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glhalleck
Total Posts: 12
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Thanks so much...ALL of you; Tom, James, Splinters.:jumpy:
Tom, if your not an educator of some sort, you should be. Your short tutorial taught me a lot. Very nicely done! I'm still sifting through it. The main thing I've learned, being the newbie I am, is start with the basics. My scene is not even near anything proportional. I tend to get carried away with this great new creative tool and loose control. Thanks again. |
Post by W!ZARD // Jun 21, 2008, 12:39am
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W!ZARD
Total Posts: 2603
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I tend to get carried away with this great new creative tool and loose control. I think we've all been there many times!! |
Post by Nez // Jun 23, 2008, 12:44am
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Nez
Total Posts: 1102
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Just to add to the above - as a TS5.x user, I thought it might be useful to show you a couple of screen grabs to help locate some of the options described in case you haven't found them already. All those colourful icons can be a bit miselading to start with - there's often much more tucked away that you can't see that you can access either with a right click or holding a left click to produce a pop-up/out menu - there's tiny red or green triangles in the corner of many of the icons to show this but they're easily missed!
Attached show how to find the panel for switching between mapped and ray shadows described above, and also how to find the render panel if you haven't found that for altering render settings. There's lots tucked away in that too, what with raytracing, anti-aliasing and more...
I thought it might also be worth confirimg Tom's encouragement to experiment for a while totry out the different lights/shadow settings - for a start, you'll probably find that some lights look better with certain shadow types, although everyone will have their own preferences... for my own part, I used to assume that because ray-raced shadows were generally described as 'computationally expensive' (i.e. slow to render) they were most accurate and should ideally be used as much as possible. I've learnt more recently that this is defintely not the best approach and using mapped shadows can give much more authentic results - with some experimentation and careful use of settings, to be sure - and I'm still only just beginning to get the idea - but for soft, fuzzy shadows they can be great. Real shadows are only rarely as hard and defined as raytraced shadows tend to be... Happy experimenting! |
Post by Steinie // Jun 23, 2008, 1:08am
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Steinie
Total Posts: 3667
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Raytraced shadows are better for sharp, crisp shadows and for transparent objects that have reflections and refractions. |
Post by TomG // Jun 23, 2008, 2:05am
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TomG
Total Posts: 3397
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There are also techniques for making soft shadows from raytracing. These have the advantage of displaying a real world feature - the further from the casting object the shadow falls, the fuzzier it is (and the closer, the sharper). This doesnt happen with mapped shadows.
BTW, before going further, Soft Shadows in V-Ray does a great job of the above too, and is my preferred solution. The next part about soft raytraced shadows is for when its not an option.
Several methods for soft shadows with raytracing exist, a search is worth it (on these forums as well as web, I remember this has been covered here before).
The first is to make a small group of lights, each with raytracted shadows. Could be four and upward. Ensure each light is close to the others, but not in an identical position. Naturally cut the intensity of each light (and the more lights you have, the lower the individual intensities for each light will be). For softer shadows, make the lights further apart in the group, but also have more of them.
All this does of course is have a set of raytraced shadows, each slightly offset, but with enough such shadows, they blend together nicely and seamlessly and look like a soft shadow. Some light types, like IBL and Area Lights, are actually groups of lights themselves, so they use this technique, only you can't control the spacing of the lights etc like you can when you make your own group of lights.
Another technique (for stills only, this would be tricky in an animation) is to have a light spin around an axis that is just a little off-center of the light (or have two lights close together, rotating around their center point). You then render using Motion Blur.
What happens here is that Motion Blur renders a set of consecutive frames, then adds them together. The spinning lights effectively create an "array over time", and the Motion Blur takes care of blending the result.
You could of course blend manually in Photoshop or similar. Also, it does mean repeated render passes for your final result, which may well be longer than using an array for one render pass, particularly where refraction or reflection are in the scene as that would all need to be recalculated each time.
So, soft shadows from raytracing is accurate, gives shadows that realistically vary in sharpness, but is computationally expensive (slow!). It's always another option to consider though, particularly when that change in sharpness depending on shadow distance from casting object is critical for the look of the scene, or you want soft shadows from transmission (glass etc), and where V-Ray soft shadows are not an option.
HTH!
Tom |
Post by spacekdet // Jun 23, 2008, 4:35am
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spacekdet
Total Posts: 1360
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Some light types, like IBL and Area Lights, are actually groups of lights themselves, so they use this technique, only you can't control the spacing of the lights etc like you can when you make your own group of lights.
Just to add to the already excellent info overload, you can somewhat control the virtual number (but Tom is correct, not the spacing) of lights in an IBL via the 'ibl resolution' parameter. Higher resolution = more lights distributed across the surface of the IBL sphere* = softer shadows = slower render.
Tip: An IBL doesn't neccessarily need an image inputted to function, but once assigned, you can't unassign an image to an IBL.
It is also my understanding that scaling an Area Light larger will in turn add more virtual lights as well. Scaling it up will a) make it brighter and b) increase the quality of the shadowing. I've always gotten the best, most realistic results using Area lights, but then again, I'm used to slow renders!
* An IBL is actually a sphere even though it's widget looks like a ring. |
Post by TomG // Jun 23, 2008, 5:09am
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TomG
Total Posts: 3397
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Ah, that reminds me of one other way! You can scale an IBL down to just a small sphere, about the same size as the 3D object for any light source. If you do that, you can lowering the IBL Samples value quite a bit since the lights are all clustered together and you probably dont need as many for smooth shadows as when they are spread wide in the "normal" use of an IBL.
You end up with a small group of lights, perfect for soft raycast shadows - this has the advantage of controlling color and intensity from one source rather than having to set it for each light individually.
There's also a plugin for controlling arrays of lights on the Model side, if you want to go the individual omni light route.
Thanks!
Tom |
Post by butterpaw // Jun 23, 2008, 5:12am
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butterpaw
Total Posts: 831
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i did not even know enough to pose this question so .. glhalleck thanks so much for asking it.. and thanks to the rest of you for answering..
now... let me go back over all that ... s-l-o-w-l-y
:p |
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