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Post by Vince De Quattro on Sept 21, 2004 11:21:08 GMT -8
Practice CG match lighting to a still BG.
Using a single capture frame (digital still camera qualifies), light a CG model to the background and then composite.
Extra credit for using rolling footage and/or CG animation.
Vocabulary
BG background (plate)
match lighting
determining the lighting conditions on the shooting stage/location and transferring this light model to either the blue screen talent or CG model(s).
plate
an image or series of images captured during principal photography (or subsequent second unit work)
principal photography
film/video shot during the initial production schedule
rolling footage
a series of still frames
second unit
a production group assigned a small portion of principal photography, often to pick up missed or poorly shot initial footage, blue/greenscreen work or any other footage not shot during the original shooting schedule
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Post by Garrett on Sept 26, 2004 9:01:37 GMT -8
Pete- Vince and I worked on a few solutions to this problem. The easiest thing to do is to enable multi-pass rendering or render layers in Maya. Make everything you want to be rendered on. Maya will automatically separate each pass in to the appropriate folders that you set as your project. Then you can bring in those separately rendered plates i to Shake or After Effects. Once inside the compositing package of your choice you can do or tweak anything relating to the respective layer. I haven't done it yet.. but it seemed pretty straight forward. I did think of another idea that may work. This idea is to make a light in Maya negative. When you do this make sure it is a point light. It will suck out the light depending on where you place it. The idea here might be to use light linking so it only affects the palm geometry then just animate it's movement so it follows the behavior of the sphere?! Again.. I haven't tried it.. but just wanted to get that idea out there.
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Post by Vince De Quattro on Sept 28, 2004 9:43:17 GMT -8
hey vince, you mentioned in me and Garett's shot that we should roto a shadow in? paint it in? it doesn't look too convincing in shake .... kinda looks like a bad shadow attempt in photoshop using color burn ... any ideas? i take so much for granted that i forget to clearly explain the process. ROTO/PAINT SHADOWS 1. create a 4 channel matte (rgba) that defines the extent of your shadow either in a single frame package (like photoshop) or in a multi-frame package (like commotion or shake/ae). building your shadow mattes in a spline based package is the best, as you can go back and modify problems if necessary. (a one channel matte is fine (alpha only), but adding the other three channels makes them easier to preview and check.) 2. use these mattes to drive the shadow. apply a gamma/de-sat operator to the pixels that will be affected by the shadow matte. 3. subtract existing shadows from your shadow matte. be sure to extract the shadows from your plates and subtract them from your shadow mattes. double shadows are not good. 4. wash, rinse, repeat.
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Post by Vince De Quattro on Sept 29, 2004 12:20:33 GMT -8
thanks for the advice vince! when saving the matte, is it a good idea to have the shadow colour also available? doin so, requires me to save it as a TGA ... while giving different results than a 1 channel alpha TIFF , which is the only format that shake will accept. it rejects TIFFs that have more than 1 layer, like R,G or B. i'm kinda getting somewhere with this, only time will tell. you're going to use the matte to isolate an area of the original plate to apply a color correction. when i specified a 4 channel matte, i meant that all channels are the same r = g = b = a. so you'll get a white image with alpha. it's easier to check matte alignment when you're dealing with all channels on. does this make sense? i would post an example, but this silly bboard doesn't support attachments.
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Post by turbokitty on Sept 29, 2004 19:27:16 GMT -8
Hey Vince, I've been trying to make a crystal ball casting caustics, but I just can't pull it off. And also I've tried to make an object with surface scattering with no satisfactory result. On the web, I've seen a lot of cool images with beautiful effects like them I mentioned above, but nothing seems to work.
Plus, I've been dong some experiment with mental ray, and I noticed something today. I probably ticked something off or on that I wasn't supposed to, but anyway, sometimes an object just disappeared in the rendered image with the shadow still showing. I believe at that time, I was rendering an object with mental ray and then wanted to see if surface scattering was gonna work, so I tweaked some value. I didn't mess with visibility attributes, I know that. Hmm..
Could it be possible for you to show us a little trick with caustics in class sometime? For instance a crystal ball? I'd love to make something cool with nice light reflection. Thanks.
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Post by Garrett on Sept 30, 2004 8:58:02 GMT -8
May be too obvious.. but I think with Maya 6 you need to use the MentalRay shaders when rendering with Mental Ray. Actually... scratch that.. I rendered something out the other day and it wasn't a mental ray shader?! Hmmmm.... well. Maybe you could try using a mental ray shader? Eh.. who knows.. I could try a test.
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Post by turbokitty on Sept 30, 2004 10:10:03 GMT -8
May be too obvious.. but I think with Maya 6 you need to use the MentalRay shaders when rendering with Mental Ray. Actually... scratch that.. I rendered something out the other day and it wasn't a mental ray shader?! Hmmmm.... well. Maybe you could try using a mental ray shader? Eh.. who knows.. I could try a test. |•G•| Yeah, I tried both ways but it doesn't seem like the type of material I used... hmm.. very curious indeed. Anyway, I found this cool caustics tutorial online, and wanted to share it with you all. www.interstation3d.com/maya/tutorials/mray_caustics/caustics_introduction.htmCheck it out, it's pretty informative. Cheers,
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Post by turbokitty on Sept 30, 2004 11:56:57 GMT -8
I followed the tutorial I mentioned above and got this result. However, the jagged edge doesn't seem to go away even with tweaking the values. Of course the picture quality is decreased due to the compression, but the shadow doesn't seem as smooth as I want it to be. The result: www.hans3d.com/images/caustics.jpgAntialias quality value I changed in attempt to smoothen the jagged edge of the glass and the shadow: www.hans3d.com/images/global.jpgAny suggestion? Thank you.
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Post by Vince De Quattro on Sept 30, 2004 15:43:30 GMT -8
Hey Vince, I've been trying to make a crystal ball casting caustics, but I just can't pull it off. And also I've tried to make an object with surface scattering with no satisfactory result. Could it be possible for you to show us a little trick with caustics in class sometime? For instance a crystal ball? I'd love to make something cool with nice light reflection. Thanks. when you're in production you don't always have the luxury of using the ray-tracing approach. it's just too costly to develop into a pipeline across many shots, not to mention the render times. so you can fake it. almost 75% of your job will involve identifying ways to cut corners in order to stay on budget. this might be one of those instances. i would simply create a light that effects the receiving surface within a faux shadow of the glass, let's say. so one light casts a shadow which you use to hold in the effect of another light which has a fractal breakup that looks enough like caustics to pass the audience's eye. this way we can avoid ray tracing and other expensive multiple ray hit refraction passes.
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Post by sachemxi on Feb 23, 2005 14:51:55 GMT -8
This post might be better asked in the week 2 section but I will put it here too.....This might be a stupid question, but Vince told our group that we can fix the our lighting in our greenscreen shot in after effects. Does anyone know how to do this?
sincerely,
Joe Zaffuto
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Post by malene on Feb 24, 2005 13:17:36 GMT -8
Dear Joe,
My group (GSO1) fixed our lighting by adjusting the hue and saturation, brightness and contrast, and color balence of the layer in After Effects. You have to use them together in the layer and adjust the effects to get the look of the light. Hope that helps! ;D
Malene A.
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