Settings for relative background positioning

Anybody have a handle on the settings for the positioning of a background in the rendering?
I find it curious that to make the pic move down, one gives the Y-off a positive number and vice versa, so I've figured that out, although I'd sure like to see some way to be more specific with the background image.........maybe be able to shift it around real-time in a mock rendering window????

I get X-off and Y-off but..........
what does X-scl and Y-scl mean?????

Chris

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Permalink Reply by Richcat on October 14, 2010 at 2:41am

Hi Chris
Funny you should mention this as I was just playing around with this to see who real a scene I could get with rendering of dragon skp with castle background, and was today going to try scaling moving the background to see the floor 0- all done in nxt no PS
I was getting some odd results in nxtimage editor, but its
probably because I hadn't realise it only works on planar It only works on planar

Offsets - for Planar Projections

* X-Offset
* Y-Offset

Scales - for Planar Projections

* X-Scale
* Y-Scale

Luv the idea of real time moveable rendering window

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Permalink Reply by Christopher Alan Krupp on October 14, 2010 at 12:15pm

Rich:

Are you saying that one can scale the image as well.....is that what sl (or whatever it is) means?
I love the idea of placing an object essentially with-in a background. Hadn't thought of that.

I have to keep running small scale check renders to figure out where the background really is. No issue with plan jane backgrounds, but those with land/sky/trees layered horizontally present a challenge.

Al: any input?

Chris

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Permalink Reply by Richcat on October 14, 2010 at 12:30pm

Chris

I don't know why but my post seems a bit mixed up, with repeats of words etc.
Too much beer!

Anyway there should be a link to the RPS wiki website where I found the info about the X and Y when reading about the background tab.

Here' the link

X-off and Y-off ( I presume short for offset) to move background around the rendering window and X-scl and Y-scl to scale the image.

For this one I just placed dragon, added background image, visible and reflective, selected ground plain on, but made ground alpha by selecting alpha on background tab. Its getting called a "shadow catcher" or similar by various other rendering engines for sketchup . A few very small few test renders to position and then render at required settings. I also made my own castle hdri identical for lighting the scene. I need to make it large to see the dragon better.

I made the HDRI with 3 different exposure shots and some other software, but I know you can make your with nxtimage editor, by rendering just background image saving as nxtimage opening in editor and saving that a HDRi, haven't tried it yet so don't know how effective its is.

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Permalink Reply by Richcat on October 15, 2010 at 4:35am

I've tried out the scaling X and Y and they have not difference, which appears to be a bug, and there other things like the reflection of the background appears not to work even if HDRI is turn off.

Image below was HDRi lit (rotated 45 to bring in line with background), with some sun and sky, background visible but no reflection. Cars probably a little big

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Permalink Reply by Christopher Alan Krupp on October 15, 2010 at 8:12am

Rich:

So you tried to scale the image and nothing happened??? Curious. Did you contact Al with that info?
What does HDRi stand for? I'm just an architect trying to stumble through this stuff and find it quite interesting. Very little else to do these days. I keep designing imaginary buildings, Ha!

I like the way you're getting the objects to look like they're in the scene. That's just the background image, right?
How do you make the background envelop the object? The car looks like it is surrounded by the walls.

I guess I'll have to do the crude trial renderings to place the background for now. Hey, where are you getting these great background images?

Chris

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Permalink Reply by Render Plus on October 16, 2010 at 2:22pm

An HDRi is a 360 degree image and is the preferred way to add "backgrounds" to a model. Actually the HDRi is a background, as well as sky, foreground, etc. for reflections.

Their are two major differences between HDRi images and other raster formats.

1. The HDRi is a full spherical image prviding background imformation in all directions.

2. In addition to colors, (red, green and blue), then HDRi image contains an additional channel which is lighting intensity.

In the image below, (extracted from an HDRi image). the white from the windows and the white on the wall below the windows (see arrows) aren't all that different in intensity in the RGB image. However, if your are using this image for a background, much, much more light enters the scene through the white windows, then is reflected from the walls. So the HDRi format includes an intensity channel which specifies that lots of light comes in through the windows.

(This is not the full HDRi image. The full image would includes all of the walls of the church - and 1/2 of the image would be the floor)

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Permalink Reply by Render Plus on October 16, 2010 at 2:27pm

Backgrounds do not effect the rendering at all. We render the scene with a transparent background, and then paste it on top of the background image.

If you want to do the same, and paste it in a paint program, which will make it much easier to align, you can leave out the background, and save the image as a transparent .PNG file.

See this article: Alpha Images Where I rendered the engine in transparent/alpha mode and then pasted it onto a background image. (It looks a little like the background is reflected on the engine, but those reflections are actually a part of our forest HDRi image used for default, High Dynamic, lighting.

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Permalink Reply by Render Plus on October 16, 2010 at 2:31pm

Richcat said:

I've tried out the scaling X and Y and they have not difference, which appears to be a bug, and there other things like the reflection of the background appears not to work even if HDRI is turn off.

Richcat,

There is a setting on the Support dialog (right click on the title bar or the rendering, or click Support on the More Setup tab), to turn off manual background processing. This will restore the nXt engine's background processing. We had turned it off because of ghosts we were getting when viewing a background through a window, when something was in front of the window.

This may make the offsets work again, and give you some reflection. I need to work with this more next week, and do a better job with background images.

Here is an example of the problem we were trying to fix:

(The white ghost lines in front of the window)

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Permalink Reply by Richcat on October 16, 2010 at 5:17pm

AL thanks for relying about HDRI info for Chris, I know how to use and create them but not all the info you have given.

I find the free ones off the internet not very good for backgrounds as they get very pixelated, and reflection can be pixelated and they tend to be very large files.
I do use hdri's for lighting, adding reflections, and tend to use a jpg image of hdri for the background.

I prefer this method of using backgrounds included in rendering, but I know what your are saying about rendering with the scene lit by hdri and transparent background and then using PS to place on an image. It would probably given a lot more flexibility for position size etc and would cut down the test renders to find out if you have it in the right place. "old dog new tricks"

I find found the setting your talking about when right clicking rendering window, it does not appear in support from more tab- I do remember the white ghosting issue from way back.

Hi Chris
Sorry not to get back to you, a bit busy with family car playing up.

Yes the image is basically just plain flat jpg background image, with skp car in middle, with the scene lit by hdri of the background image. The reflection on the car are from the hdri. Please note I have ground plain on but set as alpha, which catches the shadow of nay object in your scene , sketchup ground, sky and background are all white, and shadows on

The surrounding effect is careful placement of object, scale and perspective being v important, and getting the hri reflections on the car to line up approx with background. The way the shadows fall in the background image are very important and you need to spend time setting up your object to have the same shadow projection, and angle of lighting.

I got the images on holiday near Tenby - Pembroke Castle, set up to camera to take 3 shots automatically with various exposures and then combined them using some software when I got home. Always looking for scenes I can use, and some just because I like them- drives family mad as I tend to wait for people to not be in as they create ghost effects

Richcat

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Permalink Reply by Christopher Alan Krupp on October 17, 2010 at 5:59pm

Rich:

I tried out Al's suggestion with the transparent png thing and find it works quite well. I can now just slide the png anywhere I want on the background, crop the whole mess and viola! a finished rendering with a perfectly placed background.

Chris

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