- Mon May 09, 2011 4:11 pm
#342440
Now, it's entire possible that I'm doing something wrong but I'm sure it used to work and I'm using the same workflow as before. [I'm using the Softimage 2012 plugin with Maxwell 2.5.1]
I want to composite a Maxwell render onto a background plate, complete with shadow. I've created my model, added a ground plane with a shadow material. I've then rendered out the colour, alpha and shadow channels. I've then used Tom's Photoshop action to cut-out the colour image from the background using the alpha channel. I've added a Photoshop layer below this and filled it with white (ultimately it will contain an image). I've then shift-dragged (to make sure it is exactly centred) the shadow channel image on top of the colour channel layer and changed it's blend mode to multiply.
This should work (and I'm sure it did in the past) but there is a white halo around the resulting image, caused (I think) by the shadow channel not containing data in the anti-aliased fringes of the colour image - the shadow channel only seems to contain non-white pixels outside of the alpha channel's 'positive' (non pure black) area!?

In a possibly related issue I've also noted that sometimes the shadow channel has very strange results. In the following example you can see that there is odd shading variation in the shadow channel under the lid, bottom left (it almost looks like a reflection channel!?). The floor material is a shiny surface with the shadow channel turned on - I'm not sure if the shininess may be causing the problems? Does a shadow material need to be a one layered, lambertian mxm?


Any help on what I'm (or Maxwell's?) doing wrong would be greatly appreciated.
I want to composite a Maxwell render onto a background plate, complete with shadow. I've created my model, added a ground plane with a shadow material. I've then rendered out the colour, alpha and shadow channels. I've then used Tom's Photoshop action to cut-out the colour image from the background using the alpha channel. I've added a Photoshop layer below this and filled it with white (ultimately it will contain an image). I've then shift-dragged (to make sure it is exactly centred) the shadow channel image on top of the colour channel layer and changed it's blend mode to multiply.
This should work (and I'm sure it did in the past) but there is a white halo around the resulting image, caused (I think) by the shadow channel not containing data in the anti-aliased fringes of the colour image - the shadow channel only seems to contain non-white pixels outside of the alpha channel's 'positive' (non pure black) area!?

In a possibly related issue I've also noted that sometimes the shadow channel has very strange results. In the following example you can see that there is odd shading variation in the shadow channel under the lid, bottom left (it almost looks like a reflection channel!?). The floor material is a shiny surface with the shadow channel turned on - I'm not sure if the shininess may be causing the problems? Does a shadow material need to be a one layered, lambertian mxm?


Any help on what I'm (or Maxwell's?) doing wrong would be greatly appreciated.
Last edited by oz42 on Tue May 10, 2011 1:33 pm, edited 1 time in total.