Background Image Proportions

I’ve asked the question before, but no one seemed to have an answer. It’s pretty annoying so I’ll ask it one more time.

It’s a small problem with the background image feature. I get everything set up; the images are proportional to one another and everything seemse to work fine, but there’s always at least one image that loads too small. I try to resize it but it seems to throw the rest of the images off. I can’t figure it out. I’m sure there’s a solution to this, but I’m lost on how to find it.

Here’s an example of what I’m talking about. The mesh in this screenshot is the same cube in all four “windows”.

Please tell me what’s going on? If I can’t figure this out I might as well give up.

Okay, looking at that picture I can see that blender resizes the side-view image so it’s the same number of units wide as the top-view image. Will I have to overcome this every time I load background images?

Did you try the background image panel? Could I experiment with your .blend? (remember to pack the images!)

Blend file and images.

There you go. I’ve tired fiddling with the image panels but nothing seemed to answer my questions.

Hmm, that’s not very good is it ? I tried reworking the images in photoshop so that they were all about the same square size (by adding space around the border, not resizing the car images), but that didn’t seem to work either. Sorry, I don’t have any suggestions other than to resize the side image to be 11.5 instead of 5.0. Interestingly (or maybe not) the ratio of 11.55 to 5 is 2.31. The ratio of your 2113 pixel wide image to the 914 pixel wide image is the same ratio, so maybe that is something to do with it ? Maybe you could try resizing the images more carefully than me and get a better result ? Good luck.

Yeah, I think the ratios probably have something to do with it. But I’m pretty sure the images are sized correctly enough. Anyway, thanks for trying. :slight_smile:

Does anyone else have this problem when setting up their blueprints?

While it’s not 100% perfect, there’s a fairly simple way to do this. First, pick one of the images as your base(I used the front view), and then space your cube/plane so that it fits to the very edges of the car on the X and Z axis. Then, go to the next view(back), and adjust the size/location so that the edges of the car in the picture match up with the cube. Then fit the top and side views, so that they match along the X axis, then stretch the cube along one of the pictures so that it fits the car on the Y axis. Then adjust the other view accordingly.

I did this, and packed it all into a .blend. Like I said, it’s not 100% perfect, but it’s very close. I did a basic outline of the windshield so you could see how they match up.


Hi Hobo Joe, I think you suggestion is pretty much the same as mine - resize the side view image so that a cube fits okay. And that certainly works, however I think it is still a problem with Blender.

How is it a problem with Blender? If all the pictures are different resolutions, with different proportions, how would Blender know how to size them all correctly?

when i look a the screen shot you uploaded
none of the pic has the same scale
unless you change the scale in background panel?

search the forum for this
and i did think here was a problen with the sideview YZ but it seems that this has been corrected

to test it put a Cube and check the scale in each viewport
you will se that it fits precisely

i think this was a problen 2 or 3 years ago but it has been solved
there was a problenm with the scale for the side view and it had to do with the proprotion of the screen 640 x 480 i think
but with advent of high res screen this has been corrected

but with the latest version you don’t have this problem

the only thing is to make certain that the size and scale of your images are the same
and that the scale inside each image is the same
and this should go well for the background image
i did test that last year and it work fine

now here is a tutorial on how to set up blueprint for cars

happy blendering


Hi Hobo Joe,

to my basic thinking -> When I add a cube into the model and scale it up so that it is the same height as the car, and then scale the cube in the y axis so it is the same length as the car, and then scale in the x axis so it is the same width as the car, the front and top views appear to be fine. If I resize the side image size to the default 5.00 (same as the other views), the image is too small to match the cube. The ‘height’ of the front view image is 593 pixels, which is the same as the ‘height’ in the side view image - but they are not being displayed at the same size, even though they are both 5.00. Comparing side to top - the ‘length’ in each case is 2113 pixels, but again they appear as a different size in blender. I agree that all you need to do is find the problem view and resize the image, but I’m not clear about why one appears to be a different size to the rest. Blender doesn’t appear to be distorting any of the images, so it seems happy with them being different dimensions on the two axes of the picture. How does it decide how big to make the image when displaying it as a background image ?



i did a square with paint
and then loaded up all 3 viewports same pic
sam scale ect…

see pic

and check out the grids numbers for dimensions

they are all same size


Good tutorial too - makes it very easy to understand.

Since you went to the trouble, I thought I would experiment too - and did some experiments with Paint, using 400x400, 400x800, 400x1200 and 1600x400 (height x width). What appeared to happen is that whatever the default width of blender units Blender uses, it uses that to scale the image on, based on the width. For example, lets say that when you load a background image it appears on the screen at say 10BU wide. If you image is 400 wide and 800 tall, it will use the full 10 BU for width, and then your image will be 20 BU tall (10BU x 800/400). If you use a 400x1200 image, then the 1200 pixels will ALSO appear in a 10BU image, and then the height will be 3.33 BU (10BU x 400/1200), and if you use 1600x400, then it will be 10 BU wide and 40 BU tall. This is why TK’s side image is the “wrong” size - the width of the image is different to the rest, and why your example is fine - because they are all square.

Presumably if I had taken more care in resizing TK’s images to make sure that they were all square and of the same number of pixels, they would have all been fine. Well, I think I’m happy - I’m not sure that sizing based on width is the best way to go, but at least I understand how it seems to be working now.


Blender treats the entire width of a background image as 1 unit. 1 width = 1 blender unit always (until you scale it up in the floating window). If you pad the sides of the skinnier pics to have the same amount of pixels across as the fattest, then you’ll be working in the same scale – in your case, 2113 pixels per blender unit.

EDIT: seems Wolf figured it out anyways. The reason why Blender goes by width instead of the more direct “pixel” as a unit IMO is that both super-high and super-low resolution pics can be handled without obscene scaling values.

the [ point is that when you load pic in viewport it uses the same scale to start with
so i redid a test wiht what a rectangle instead of cube


now one thing which is wrong here is the fact that the side view pciture is the same than the other one which in my case is wrong because i used the same pic
and that may confusing a little

and in reality the depth of the object is larger than the pic i use!
but look at the yellow cube i did around the pic

you get the same dimensions in BU eveywhere as long as the size of the pic is the same and you use the same scale inside the pic you’ll get the exact dimensions
of you model in all viewport

it odes not mater how blender show the pic the scale is preserve base on the size of the loaded pic in pixel or whatever other measured value you use

so eveything is fine and work properly there are not bugs there


Greetings. If I understand your last post correctly, each of the images has the same ‘width’ and so you don’t see any problem, as it appears that Blender sizes the image based on fitting the image into its standard width. And you see no problem. I’m not sure that I would describe the situation as a bug, but as a sub-optimal interpretation.

As I see it, the main reason for having background images is to assist with modelling to a given scale from a set of blueprints. Now, to me it is reasonable to think that someone may have created cut down front, side and top views from one drawing. As such, all drawings will be to the same scale, but they will likely have different dimensions in ‘x’ and ‘y’. For my money a better ‘interpretation’ would be to perhaps scale the first image to fit the normal 10 bu, but to consider the pixel size and use this for subsequent images. Eg first image is 400 pixels wide by 800 tall. That gets sized at 10 BU wide, and 20 BU tall ( no stretching). If the next image is only 300 pixels wide, instead of scaling that to also fit 10 BU as well, it would appear as 300/400 x10 BU, ie 7.5 BU wide. That way no views would need to be resized.

Is there any obvious flaw in the logic that anyone can spot ?



So what happens now?

If this is really meant to be a feature of Blender, it’s a very confusing and frustrating one, especially for new users.

you could also search this forum and find there is a lot of post about this subject

and there are no problems as i know of for background size or scale pic

as you said use the way you like to work with
the point here is if you begin to play with scale you better understand carefully
to get good results

i the pic i’v show look at the added yellow square and the corresponding dimensions compared to the size of the background pic and grid also and it fits precisely
there are no errors on the scaling or dimensions

may be your eye perceives a difference but that;s not important
the important thin is to
be able to draw lines that are at the proper scale function of the lines in the background image and eveything will fitt precisely and give the proper dimensions
in the model

but be carefull to the fact also that if you are using a very small scale the errors you do are larger than in a large scale background pic
but this is tru for evey DWG that exist

that’s why normally in industrial drawing you do not measure lenght on the DWG per say but read the indication of lenghts that are marked up on the DWg
this is the only way to get the real value

so tracing along a scaled model PIC will always give some errors and will always
be an approximation tio the reals thing
unless you have precise dimensions to set the different parts of your model

in conclusion there are no bugs for the scaling or dimensions of background pic inblender

by the way make certain that yall your viewports are in ortho mode
not in perspective mode !


I think you should read WolfOfBadenoch’s last post. He disagrees for the same reasons I do. But I’ll just learn to live with it for now.

I may post another example later. Until then I’ll do a little searching.

The changes made in the image panel should only apply to that specific image. I’ve never even heard of this happening. It’s an interesting problem; as frustrating as it must be for you. I hope you find an answer.

I found the background feature useless as implemented for all the reasons you mention. Beside, you need to have all your windows setup once and for all and never touch them or, even worse, close them. The best alternative I found is to map images on planes and use those mapped planes as references. Those planes must be different objects. You must then work in texture render mode and it is possible to play with the different object specific Draw modes to see through the object being modeled while still seeing the images on the mapped plane. That is a little cumbersome but at least usable. One benefit of this technique, though, is that you can position planes in any other way than orthogonal to the Z, Y, and Z plane and have 3/4 view references, for example. If each of your planes are different objects, then you can turn them ON or OFF in the outliner or place them in different layers and turn them ON/OFF this way.