[Mihai]

So as mentioned in the first post, here is a set of 5 free HDRs (including the 3 used above), for anyone that has purchased or will purchase anything from the Maxwellzone store.

These are 3500px width. They don't include any backplates or textured road surface. But they are still perfectly usable for lighting purposes.

http://www.maxwellzone.com/shop/5-free- ... customers/

[Rafal SLEK]

So as mentioned in the first post, here is a set of 5 free HDRs (including the 3 used above), for anyone that has purchased or will purchase anything from the Maxwellzone store.

many thanks!

[choo-chee]

Thanks for the feedback - in your usage case does it matter that you have back plates to go with the HDR, or not so much?

backplates are not necessary as I have accumulated 100's and 1000's over the 20+ years I work in arch-viz.... but never seen a really good urban HDR, in the style I've mentioned.

[Mihai]

Yes, it seems back plates are mostly useful for automotive rendering.

Btw, there was a problem for customers with the download link on the blog post page, please try it again, should be ok now.

Got "busted" today trying to photograph in a mostly empty parking....after letting me take all the photos. Nice

[Mihai]

With an HDR that has many small strong light sources, it becomes more efficient to blur slightly the HDR used for the illumination slot. In this example I only blurred the map with a 4px gaussian blur (for a 7000px wide HDR map, if map is smaller, a smaller size gaussian blur would be enough). It only slightly affects the sharpness of the shadows. You can see how much noisier the non blurred version is (both @ SL18). Make the browser window wider to see the full size.

[Mihai]

I like the lighting from this one. Mellow magenta sunset.

[Fox2]

Nice job Mihai!

Really like the last one too

[feynman]

Yes, it seems back plates are mostly useful for automotive rendering.

Not at all. Industrial designers who do outdoor products, sports equipment, public furniture, bicycles, gardening tools and much more are in dire need for suitable backplates onto which they can render.

I never got backplates to work right in MR though. Background, Reflection, Refraction and Illumination only accept HDR images and Screen Mapping affects all four slots. There should be something in the MR documentation that shows how to do a proper render on top of an undistorted backplate. Or is this explained properly somewhere?

For Maya using Mental Ray, it is well explained how to set up the HDR dome plus backplate to match the camera also.

[Mihai]

Thanks for the feedback, it makes sense and I can see a need for urban type stuff developing not just for cars, but for electric bicycles, scooters etc...

About putting a rendered item into a backplate photo, this is not something you want to do "in render", because you do need to color correct the render to match the photo, at the very least setting your white and black point to match the photo, remove/add some color cast etc. I will do a tutorial on Maxwellzone for this but in short:

- for the best match you add a ground plane with a texture derived from the HDR. If you don't have such a texture just add something similar. You need a ground plane for 1. as a shadow catcher, and 2. to have accurate reflections and light bleeding on your model and not just have light coming from underneath a dome that surrounds your scene.

- add the HDR to the background slot and set all other slots to "Same as background". Activate the view of the HDR in the background (in Studio this is with Ctrl+K), and rotate it until the view matches more or less the background photo you intend to use for compositing. This is to match the lighting and reflections.

- on the material applied to the ground object, you turn on Shadows, from global properties.
- the plane object itself, you hide it to camera.
- for all the objects sitting on the plane, you turn on "Hide to camera in shadow channel". This way you get a "full" shadow channel and avoid having a white outline when compositing.
- turn on Shadow channel and Alpha in Render options, and I suggest to render the output as PSD, 16bit and set the channels to be embedded. This way you get a PSD file where your object(s) are already cut out using the Alpha, and your shadow pass is also present, all in one convenient file.

To composite into the background photo:
- if your photo is just a jpg 8 bit, switch it to 16bit just so you can paste in your render and still make adjustments to it in 16bit.

- in the PSD, select the render layer that contains all your cut out items, and (at least in Photoshop), go to Layer>Matting>Remove black matte. This will remove a black border around your items (it will really remove black from any semi transparent areas in your render, including glass, and antialiased areas (borders) are semi transparent because of being cut out from a black&white alpha which had antialiased borders).

- copy paste the background photo into the PSD file. Put the shadow layer beneath the render layer, and set it to Multiply blending mode. It's important to correct the shadow layer with curves and maybe adding a hue to it, depending on how the shadows look in the photo. You will see in reality shadows are hardly ever completely grey, use the color picker to examine their hue. Your rendered shadows will most likely need darkening because of the linear output from Maxwell and also the real photo may have been developed with some heavy contrast.

- now you adjust the main render with levels, curves, color balance etc. to make it match as best as you can with the background photo.

Ideally the background photos taken at the same time as the HDR, and the HDR, have been white balanced to about the same values. You may still need to do a bit of tweaking by eye to match with how the photo was developed, which contrary to the linear HDR, may have had a certain camera profile added to it, and other adjustments which can alter its white balance a bit.

Btw, that tutorial you linked to is detailed but not too universal or easy. Besides knowing Maya, you also need to know Nuke to follow along...two already pretty complex apps, and the camera matching by eye is always a frustrating experience. This is why I'll try to provide files which contain the camera positions already.

[Nasok]

Nice HDRI )
There are a tons of free and paid HDR images out there on web but, for sure the high quality ones (like yours) are a point of hunt

Especially if they have a though process behind, not just forest or mountains, but rather designed to be as generic as possible to fit most of the scenarios and also to be as specific as necessary to get that connection with the backplate.

Great work, man!
As always.
T.

[choo-chee]

very nice, still as far as I've tested, HDR are nice but only for cars and reflective objects. typical exterior and esp. interiors do not benefit from hdr that is more noisy, at least for what I've tried. I tried regular hdr, "enhanced sun" hdr, blurred hdr... physical sun is always a bit slower but also less noise at high SL....tried to use a "fake sun" emitter, worse than real sun. would be glad to find how to use HDR with speed, not only good reflections...

[Javi Antúnez]

Mihai, have you ever expirenced fireflies with sunny HDRIs?
We do the HDRIs as you do, but sometimes we end with fireflies like the image attached.
Maybe the shader?

Thanks!

[Mihai]

If the sun is very strong (so very small sundisk) I do get fireflies on some reflective surfaces but I think these are reflected caustics. If I do get them the Dust & Scratches filter in Photoshop (under the Noise filters) helps to remove them quite nicely (and you can always make a selection based on matID channel, objID channel etc.). Use a radius of 1 and raise the Threshold until most dots disappear and you have the least blurry result.

On your example though it looks more like metal flakes reflecting in the paint rather than fireflies? Fireflies tend to have the same size and almost the same intensity.

[Javi Antúnez]

If the sun is very strong (so very small sundisk) I do get fireflies on some reflective surfaces but I think these are reflected caustics. If I do get them the Dust & Scratches filter in Photoshop (under the Noise filters) helps to remove them quite nicely (and you can always make a selection based on matID channel, objID channel etc.). Use a radius of 1 and raise the Threshold until most dots disappear and you have the least blurry result.

On your example though it looks more like metal flakes reflecting in the paint rather than fireflies? Fireflies tend to have the same size and almost the same intensity.

We've seen that it happens with small sundisk, but we need sharp shadows... Is there a better way?

[Mihai]

Try blurring the HDR just a little bit, 2-4px gaussian blur. Shadows will still be pretty sharp but the fireflies might go away.