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  1. #1

    Question about Shadows - Depth Map vs Ray Trace

    OK, so just what is the difference between Depth and Ray Traced shadows? I mean from an 'artistic' view and from a 'funtional' view and what are the 'trade-offs' conserning Poser6 performance?

    I tend to use RayTrace shadows a lot but have found that a scene with transparancies (like Traveler's Grassy Crop) it can bring Poser to a Dead Stop, yet if I set all shadows to Depth Mapped then the scene, with same lights and other settings, will render on through.

    So, by Not using RayTrace shadows but still rendering with the RayTrace engine, exactly what features can I expect to loose (ie: mirror, various material room funtions, Face-Off's python script for RealSkin, etc)?

    And why does RayTraced shadow bring Poser to a crawl/stop where Depth Mapped shadows do not?

  2. #2

    Re: Question about Shadows - Depth Map vs Ray Trace

    Thank you for asking that, igohigh!
    I had several situations where I would set all the lights to raytrace (or was it depth map...can't remember now) but I would get no shadows at all!
    So I was going to ask the same question, only from the stand point of asking why I wasn't getting any shadows a lot of the time when they were showing in preview.

  3. #3

    Re: Question about Shadows - Depth Map vs Ray Trace

    Well I do know the 'preview' shadows are not the actuall previews of the Lights themselves, more of just a general idea...to what purpose?
    I always used RayTrace because I seem to get the best shadows with them, but when there is a lot of Transparancy to be rendered (especially glass, etc) then Poser just can't handle it, so I was wondering just what the 'descriptive' details of the two types of lights are and what features require RayTrace Shadows as opposed to just RayTrace Engine when rendering...

  4. #4

    Re: Question about Shadows - Depth Map vs Ray Trace

    My understanding of this is that if you use depth mapped shadows (which uses shadow maps) then the raytrace engine is still there to give you nice reflections and ambient occlusion etc. Shadow maps tend to be less accurate than raytrace shadows, but render faster (depending on the size of the map, which you can alter). Raytrace shadows have a harder edge whereas you can easily achieve soft edges with shadow maps.
    As to what features specifically require Raytrace shadows in Poser I'm not sure, although this is the case with other 3d apps I've used.
    I actually haven't used raytraced shadows at all yet in Poser, and I've had no problems getting reflections, refractions, ambient occlusion etc. Volume effects might be different, but I haven't tried any of that yet.

  5. #5

    Re: Question about Shadows - Depth Map vs Ray Trace

    "depth mapped shadows (which uses shadow maps)....(depending on the size of the map, which you can alter)"

    OK, what am I missing? How do you control the 'size of the map'?

  6. #6

    Re: Question about Shadows - Depth Map vs Ray Trace

    In the light pallet under "Others" is the map size. Change the map size to a higher number, will slow down the render and give better shadows. I.E. 256 to 512 to 1024.

  7. #7

    Re: Question about Shadows - Depth Map vs Ray Trace

    "Use raytracing":
    This is a render option that will define weather or not the render engine will use raytracing. What does that mean?
    It means that if you do not check this option, any special effect requiring raytracig won't render. It applies to raytraced shadows (wich could explain you don't get them sometimes), reflections (not reflection maps, ok?), refraction, AO, Fresnel node for example.
    If your scene do not use any of these features, you may uncheck the option. If it does, let it checked.

    "Raytraced shadows" vs "depth map shadows":
    This light option defines the process (or calculation type) that will be used for shadow casting. Raytraced shadows are much more accurate, precise than "depth map" shadows (which tend to be a bit soft and blurry).
    So, if you want a soft lighting in your scene (a lamp with a paper/cloth cache for example) you'd better use the shadow map option. You can define its sharpness by entering a higher shadow map resolution. Lower resolution will produce softer shadows (in shape).
    If you want a hard light, such as a sunlight, then you'd better use the raytraced shadows option. There is a blur option that will allow you to get softer shadow edges as the distance between the object and its shadows increases. It is a P6 feature very useful.

    A tip about the "bias":
    With shadow mapped shadows, use a 0 bias value.
    With raytraced shadows, DON'T! Use values between 0.25 and 0.75, knowing that the lower is the better. The value will depend of the meshes present in your scene. Some will render correctly with 0.25 as some others may give black artifacts with 0.5, so test, test and test. ;)

    I had something else to say, but I forgot what it was! :)
    Anyway! Have a look at the tutorials in the P6 ressources. Some deal with the lighting in P6. You may be interrested. ;)

  8. #8

    Re: Question about Shadows - Depth Map vs Ray Trace

    Ah! I remember!
    Shadow maps use much more memory than raytraced shadows. And the higher the resolution of the shadow map is, the more memory will be required. So be very carefull with them!
    Raytraced shadows on the contrary will be very cpu eaters during the render. Remember that you can decrease the raytrace bounce in case of problems: less rays casted so less calculation. ;)

  9. #9

    Re: Question about Shadows - Depth Map vs Ray Trace

    So depth map shadows eat Memory where raytrace shadows eat CPU? Is this correct?

    And when you say "DON'T! Use values between 0.25 and 0.75, knowing that the lower is the better."; does this mean use a value

  10. #10

    Re: Question about Shadows - Depth Map vs Ray Trace

    It is correct, yes.
    About the bias, read :
    "With shadow mapped shadows, use a 0 bias value.
    With raytraced shadows, DON'T!"
    Meaning "don't use a zero bias value with raytraced shadows". ;)

  11. #11

    Re: Question about Shadows - Depth Map vs Ray Trace

    OK, so NO zero bias on RayTrace. got it! ;p

  12. #12

    Re: Question about Shadows - Depth Map vs Ray Trace

    When using raytraced shadows with a blur radius setting (which I really like now I've played with it), is it possible to eliminate the dots that appear in the soft shadow areas if larger values are used?
    I've tried lower shading rates, higher raytrace bounces and higher pixel samples but it didn't really help.
    I also used a higher texture sampling rate but this softens everything.

  13. #13
    The Grim Reaper relik's Avatar
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    Re: Question about Shadows - Depth Map vs Ray Trace

    Raytracing is generally more realistic, however, many designers will opt for shadowmapping because it ordinarily will take less time to render based on similar settings.

    Shadow maps are calculated and saved into RAM, so if you have several lights, complex geometries, and large (hi-res) textures, you can very quickly run out of RAM. In theory ray tracing will resolve the problem but take longer to render. In some of my work, neither solution was capable of ever finishing, but these were extreme files. -R


  14. #14
    The Grim Reaper relik's Avatar
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    Re: Question about Shadows - Depth Map vs Ray Trace

    And to add, transparency will operate without raytracing in Poser, but transparency with refraction will not.

    General transparency is a value ranging from "clear" to "opaque". Basic flat window glass can usually be simulated reasonably well in this way simply with a shiny highlight, and possibly a mapped reflection. It's not photorealistically accurate, but it's suitable for most instances.

    Refraction is the bending of light through a medium, which can be anything from curved glass to diamond. In order to calculate the amount of bend, a ray must be shot from the light source, hence ONLY ray tracing will work with this.
    A water glass with only transparency and highlights will very quickly inform the viewer your image is "artificial".

    The same is the case for ray-traced reflections, where the reflection surface is calculated with respect to the physical location of reflected objects. A reflection map is calculated based on an infinite sphere that surround the entire space, and is great for irregular surfaces where a "perfect" reflection isn't required.

    However, for accurate reflections, particularly in animation where an object or objects may move in front of the reflector, the need to calculate dynamically is paramount. The same of course, can be said for refraction.-R

  15. #15

    Re: Question about Shadows - Depth Map vs Ray Trace

    relik; now as I 'think' I now understand, this would be dependant upon the Render option of 'Use RayTrace' but doesn't require a light to be set to RayTracing shadows, correct?

    I always thought at least one light had to be set to RayTrace shadows but if I understand this thread correctly then that is not the case?
    Render option "Use RayTrace" and light option "RayTrace Shadows" are independant of one another and materials only need the Render engine option?

  16. #16
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    Re: Question about Shadows - Depth Map vs Ray Trace

    That's how I understand it.

    To get reflections and refractions that are raytraced, you need to use the raytrace nodes for each in the materials room, and apply it to the proper channel in the shader tree.

    AND then you have to turn on "Use Raytracing".

    As I understand it, if you have depth mapped shadows on the lighting, the raytracing operation applies to the material effects and not shadows. HOWEVER, it will calculate the rays from ALL the lights in the scene (or at least it should).-R

  17. #17
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    Re: Question about Shadows - Depth Map vs Ray Trace

    Just re-reading your post.

    If you choose to use raytraced shadows by the setting on the lights, then YES you have to choose "Use Raytracing" (You also have to choose "Cast Shadows", but you knew that right?).

    If you have raytraced nodes in the materials (reflection/refraction/infandibulation, etc.) then to get that effect, you have to turn raytracing on, or you get blotto.

    If you have depth mapped lighting, and no raytraced nodes, then you can turn raytracing off. -R

  18. #18

    Re: Question about Shadows - Depth Map vs Ray Trace

    Render options are global, Jeff.
    So, the "raytraced shadows" is dependant to them. :)
    The render options control everything in the render as a Master. Specific material nodes or light options are Slaves. Sometimes nothing beats a sado-masochist point of view! :D
    The deal is: if something uses a raytrace feature (node or light), then you should use the "raytracing on" render option. If nothing uses it, then it's simply useless and it makes no big difference to use it or not. No difference at all. ;)

  19. #19

    Re: Question about Shadows - Depth Map vs Ray Trace

    It was mentioned, that shadows are either RAM or CPU intensive.
    Which may lead to a scene not rendering.
    A possible solution to this is using Poser 6 feature of rendering a shadow pass.
    There is an option in the render settings... "shadows only".
    You'll have to do a second regular render with "cast shadows" deactivated.
    That's how I got a render finished that wouldn't.
    All I need to know now is, how best to combine those two renders in Photoshop :D

    Martin



  20. #20

    Re: Question about Shadows - Depth Map vs Ray Trace

    Hello Olivier,

    I've been playing with and getting light settings straight myself just lately. Must say that for a final render I always raise the shadow map size to at LEAST 512 on at least a Key light. Often times a Fill light can get by with the default 256.

    You said earlier that AO does NOT function without Raytracing activated? I am working two files now, multiple image frames per file, and am using IBL with AO and I haven't activated raytracing. I didn't have reflective or refractive surfaces and know that raytracing can seriously effect render times ... Are you saying I should go back, turn on raytracing, and compare output files? The shadows look pretty good to me now with the blur radius I'm using. The idea with some of my more recent work is to milk more of the functions of P6 out of the software and see what it (I) can do.

    Best Wishes, you are an invaluable resource and boon to the Poser Community.

    Rance

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