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Hello,

how /where can I define a backplate (in my case preferred as jpeg)?
Or is this only possible with a spherical hdr, mxi or exr for IBL?

Alain

load a background image (hdr, exr or mxi) and tick "Screen Mapping" a little above in the same panel (in Studio)

h/

You need to convert your backplate image into an exr or hdr first to be able to load it in the background channel. But a much preferred workflow is to instead render an alpha and shadow channel and composite your images in Photoshop. Don't 'fix' your backplate to your render.

http://support.nextlimit.com/display/ma ... ha+channel
http://support.nextlimit.com/display/ma ... ow+channel

Mihai,
I think you are only partly correct in your comment about the alpha channel.
When we create photomontages for architectural projects and use the alpha channel to "clip" and insert the model into our photomontage, we often have an outer edge of pixels which have a slight remnant of whatever background they are rendered against. So if we can insert our background image for the final photoshop composition at the rendering stage then this outermost boundary of pixels will blend more accurately when we import and composite in photoshop using the rendered alpha channel as you suggest. I am not sure if Alain is doing the same type of work, but to me it seems likely that others would also need this function, ie to be able to position an image behind our model without having to convert it to a hdri and also without it having any affect on the lighting of the scene. At the moment we are having to apply our photos to a plane object and that's fine but time consuming to apply the material and adjust it to scale so it fully and exactly fills the camera's field of view. Obviously if there was an option to insert a backgound image (jpg) to the option within the "image based environment", then this would solve the problem. So, in short, please add support for jpg files in the image based enviroment options.

Also, maybe you can check this glitch; If I try to output an aplha channel at the same time (ie I tick the alpha channel option) then a hdri set as the background using the "image based environment" becomes invisible in the normal "R" channel. All other channels do not seem to affect it, but if the alpha channel if selected for output the background hdri dissappears !!

Sorry about the long post, I hope you can see what I mean, but if not please just ask.
Thanks

Jesper

Jesper Pedersen wrote:we often have an outer edge of pixels which have a slight remnant of whatever background they are rendered against.

But this is exactly why you should render against a black background (and why you get a black background with the alpha channel turned on), if you take a look at the first link I posted regarding the alpha channel (look towards the bottom of that page for an explanation).

Your current workflow is not very efficient and you are stuck with a background fixed to the render instead of freely compositing any background you want and separately adjusting the background and the render.

I sometimes like to use a backplate for positional reasons when I need to composite a render into a specific photo environment. Although I'll always render it with an alpha layer and cut it into the image in the end, getting that initial position can be difficult if you do it by eye and made a lot easier when you have a backplate. In this case, you'll need to do what Hervé originally suggested of converting your jpg into an mxi or hdr file. The easiest way I find is to open up Maxwell Render, go to File > Load Image... and pick your jpg image, go to File > Save Image... and save it as an mxi or hdr.

In Studio you can now set your environment to IBL and load your new mxi image into the Background section. Hit Enable and Screen Mapped and it'll show you the image as you need it (make sure it's scaled/cropped to the cameras resolution size beforehand to avoid distortion).

Hi Mihai / Rob,

Thanks, yeah I see what you mean, that'll definitely help to eliminate the white edge we often get.

Jesper

Rob, doing that in Studio is really the last place I'd try I think all 3D applications connected to Maxwell (except possibly Solidworks and Rhino) have pretty good camera matching tools, which would give faster and more accurate camera settings than doing it by eye in Studio, even with a backplate as a guide.

Mihai wrote:Rob, doing that in Studio is really the last place I'd try I think all 3D applications connected to Maxwell (except possibly Solidworks and Rhino) have pretty good camera matching tools, which would give faster and more accurate camera settings than doing it by eye in Studio, even with a backplate as a guide.

Indeed. But as a SolidWorks user myself the Studio is definitely the better option. :p

I wish I could camera map the back plane into the scene so I could make the floor really the floor and the wall really the wall, etc, for purposes of accurate reflection placement and other things.

Jfrancis, you can do exactly that...

First, place the maxwell scene object at the position of your camera (try and have the camera at the same height as the camera which made the hdr. Then map the hdr spherically onto the ground plane, using the same position for the tex coords and rotate the map to match the background, (you may need to flip the mapping)

If that works you can now camera project the backplate onto the ground plane in order to find the cam position that the backplate was taken from. Its tricky the first time you do it. heres an example.

eric nixon wrote:Jfrancis, you can do exactly that...

First, place the maxwell scene object at the position of your camera (try and have the camera at the same height as the camera which made the hdr. Then map the hdr spherically onto the ground plane, using the same position for the tex coords and rotate the map to match the background, (you may need to flip the mapping)

If that works you can now camera project the backplate onto the ground plane in order to find the cam position that the backplate was taken from. Its tricky the first time you do it. heres an example.

Does that assume I have a spherical panorama?

Is there any other?

Interesting. I'll look into it, but I'm mainly talking about camera projecting a rectangular image into a scene onto matching geometry.





http://www.digitalartform.com/archives/ ... cti_1.html

Then you could float a silver torus around the box and the reflections in it would seem faithful to the scene even with objects close by.