Headaches with Texture Mapping Coordinates

#1

For 24hrs now, I’ve been trying to get a Grille unto a gate frame (without actually modelling the grille – 'cos that will drastically increase the amount of verts in the scene … and you know what that means). I usually achieve this in MAX by mapping an alpha texture of the grille unto a plane.

So, far doing the same thing in Blender 2.5-Beta has been serious pain. The lack of documentation (that is easy to access) is killing me. I have an alpha texture assigned to the alpha influence and so far transparencies render correctly (arrggh … a bit jaggy, but I think a change in the sampling rate can fix that).Frustration begins with any change to the mapping size. Results seem unpredictable … :argh:

The default is (1,1,1). Increasing those reduces the size of the map but not proportionally. Why is that?:hmm: What am I doing wrong? As the reduction increases so does the anomaly. The opaque areas start to dominate leaving you with a very opaque mesh - and no grille.:smiley:

See Blend file

#2

Your grill object is HUGE something like 60 meters.

For a repeating texture, change the repeat value to fit your object.

For an image that has no alpha channel but is effecting the alpha value do not set “use alpha” or “calculate alpha” under image sampling. The image will modify the alpha value set on the base material of the object where the transparency is defined.

Lastly overlapping edges, with lots of tris are going to be a problem with this object. If you don’t get rendering artifacts I’ll be surprised. Simplify your test and things will be much easier.

#3

Blender has quite good documentation on its site. Problems with mapping are hard to comprehend. If you want to scale mapping just a little use [T] while object selected. Fighting with jagginess might be a bit harder as Blender uses mipmaps. First try to set FullOSA in material. Should increase render time. If it helps it is good. If not turn it off, go to texture and unselect mipmapping. Should increase render times also. If it helps it is good. If not enough do both but render times will increase a lot.

#4

No, its 15BU along X, 2.4BU along Z. Multiply that by 1000 and you get metres. The geometry was drawn in AutoCAD to live millimetres then exported to 3ds. I scaled it down by 0.001 to fit blender’s clipping extents.

For a repeating texture, change the repeat value to fit your object.

This is where I messed up … :eek:. I was manipulating the size. Do you know where I can get the documentation on this UI?

For an image that has no alpha channel but is effecting the alpha value do not set “use alpha” or “calculate alpha” under image sampling. The image will modify the alpha value set on the base material of the object where the transparency is defined.

I think I get the concept of “use alpha” (as in, use the alpha in the image if it has one) but I’m still not clear about “calculate alpha”.

Lastly overlapping edges, with lots of tris are going to be a problem with this object. If you don’t get rendering artifacts I’ll be surprised. Simplify your test and things will be much easier.

Well, I’ve not seen anything worrisome from the renders except the Grilles.

#5

So 15 x 2 meters is the correct size for this grill? Try the units setting under scene properties.

As your in 2.5, right click an item and choose “view docs” else use the Blender wiki… it’s pretty much all there.

Ahh… look again at your topology. Frankly its a mess. You can pretty much grab a random edge - move it and find doubled edges all over the place.

If this were cleaned up, I’d suggest you just quickly UV unwrap it to handle the mapping.

#6

Hi i cleaned up the mesh a little, have a look to.

http://www.pasteall.org/blend/3341
Rename it.

Cheers, mib

#7

It only confirms what I said. Changing from Blender Units to Metres only shifted the decimal point accordingly … the values are same

As your in 2.5, right click an item and choose “view docs” else use the Blender wiki… it’s pretty much all there.

Yeah right, … its descriptive enough for hackers especially those at #blendercoders IRC channel. A decent documentation will show you images (screenshots, if necessary) to expatiate on the process and results

Ahh… look again at your topology. Frankly its a mess. You can pretty much grab a random edge - move it and find doubled edges all over the place.

You are right but I don’t think I have that kind of time. I’m dealing with a lot of faces here. The Grille is only a small part of the scene. I’ll hang the blame on Autodesk’s implementation of 3DS exports. It doesn’t resolve faces to quads … mainly Tris. Funny, the weld threshold was set to 0.001.

If this were cleaned up, I’d suggest you just quickly UV unwrap it to handle the mapping.
That is a killer approach … something I do only for organic models. Well, yep … I’ll do that for objects with special images too, like an Ad post or object with stickers. But for buildings, I’m manage the generated one.

#8

See my reply to phil3d’s post above. Thanks for the example

#9

hahahaha! … cough My capacity for profound stupidity never seizes to amaze me. After 2days into the Blender study, I can’t believe I wrote that. Thanks mib2berlin, you actually pointed the way … I only discovered the method recently – a simple case of ALT+J to convert Tris to Quads (followed by delete doubles)

#10

Can’t be bothered to open up blender and test, but if I’m thinking of the right feature here, I think this should be renamed to “Use/calculate value as alpha”.

that is to say the image textures pixels/texels value is used for alpha mapping,
that is to say for rendering alpha transparency the image is converted to grey-scale.

it is a useful feature if your using one texture map to both give color(hue/saturation/not value) to lets say a low poly window class, and then the value of the pixels/texels is used for transparency. :slight_smile:

hope the explanation makes sense. :slight_smile:

Yeah right, … its descriptive enough for hackers especially those at #blendercoders IRC channel. A decent documentation will show you images (screenshots, if necessary) to expatiate on the process and results

yeah, I think that feature(that is to say the actual documentation[generated?]) is actually unfinished still… :slight_smile:

#11

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