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(I have updated this thread to suit the latest release of Vray - to avoid confusing people with references to 'linked materials' etc which is now redundant - David)
Further to this thread http://asgvis.com/index.php?option=c...20539#msg20539 regarding different background solutions
HDR skies are ok but are unlikely to be specific to your site.
Site photos are ok, but are not hdr, so difficult to get them to 'emit' in the sky area and not 'emit' in the non-sky area, so they are less than perfect backgrounds.
SOLUTION
On location, take photo at 180deg to the intended photomatch view (or take several and stitch together) - image 1
Make an alpha map of the sky - image 2 - note this alpha map is inverted - so check the 'invert' box when inserting the map in the transparency slot.
In sketchup, set up billboards opposite the model to provide reflections - that is IMPORT image ('use as image') - then explode. You will now see the image appear in both the SU material editor and the Vray materail list. (set horizon of images to match model) - image 3
set transparency of billboard image to 100%
create vray linked material of image,
If you want the billboard to be emissive (it may otherwise be poorly lit and dull if the sun is behind it)
then put ( image 1) in a new emissive layer (at say an intensity of 3 for physical camera)
put alpha map in transparency slot of the same emissive layer
Use your 'favourite' hdr sky (or just the vray sky)
RENDER
This allows the sky to be bright and the non-sky areas to just act as skyline as this final image shows, but I realise this might be a sledgehammer to crack a nut(!).
Hope this is helpful
David
Image 1 - site photo
Image 2 - make alpha map
Image 3 - sketchup set-up
Image 4 RESULT
Image 5 Orginal photomatch image
Just to round it off - the background will cast a shadow, but only the non-sky area, so you don't get the usual rectangular shadow that you often get with a regular billboard. This means you can sometimes use the shadows to your advantage. (I've put a plane in front of the billboard here, just to show the shadow result ;D
Further to this thread http://asgvis.com/index.php?option=c...20539#msg20539 regarding different background solutions
HDR skies are ok but are unlikely to be specific to your site.
Site photos are ok, but are not hdr, so difficult to get them to 'emit' in the sky area and not 'emit' in the non-sky area, so they are less than perfect backgrounds.
SOLUTION
On location, take photo at 180deg to the intended photomatch view (or take several and stitch together) - image 1
Make an alpha map of the sky - image 2 - note this alpha map is inverted - so check the 'invert' box when inserting the map in the transparency slot.
In sketchup, set up billboards opposite the model to provide reflections - that is IMPORT image ('use as image') - then explode. You will now see the image appear in both the SU material editor and the Vray materail list. (set horizon of images to match model) - image 3
set transparency of billboard image to 100%
create vray linked material of image,
If you want the billboard to be emissive (it may otherwise be poorly lit and dull if the sun is behind it)
then put ( image 1) in a new emissive layer (at say an intensity of 3 for physical camera)
put alpha map in transparency slot of the same emissive layer
Use your 'favourite' hdr sky (or just the vray sky)
RENDER
This allows the sky to be bright and the non-sky areas to just act as skyline as this final image shows, but I realise this might be a sledgehammer to crack a nut(!).
Hope this is helpful
David
Image 1 - site photo
Image 2 - make alpha map
Image 3 - sketchup set-up
Image 4 RESULT
Image 5 Orginal photomatch image
Just to round it off - the background will cast a shadow, but only the non-sky area, so you don't get the usual rectangular shadow that you often get with a regular billboard. This means you can sometimes use the shadows to your advantage. (I've put a plane in front of the billboard here, just to show the shadow result ;D
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