[Soc-2017-dev] vertex paint project - ply exporter

Darshan kadu darsh7807 at gmail.com
Tue Jul 25 19:41:15 CEST 2017 

Hello, Mr. Howard,

I can't create video now(the internet is too slow to download software for
that and upload video),
I did this to bake vertex color to PNG.
-->set  mode as UV editing
--> select the mesh in edit mode, press<space> select mark seam.
-->press<U> select unwrap
-->in render tab go to bake select bake mode to vertex color
-->bake color
-->come back to UV you will get color on uv.
-->save it as png file

One thing I Notice if I use this png file then to bake vertex colors then
the alpha was properly assigned,
but if I use the other png file which I took from the internet alpha was
not getting properly assigned.


On Tue, Jul 25, 2017 at 5:24 PM, Howard Trickey <howard.trickey at gmail.com>
wrote:

> Darshan,
>
> I'm sorry, I'm not figuring out how you did that (baking vertex color to a
> PNG file).  Could you explain the steps your followed in detail or maybe
> make a video showing how you did it?
>
> On Tue, Jul 25, 2017 at 6:35 AM Darshan kadu <darsh7807 at gmail.com> wrote:
>
>> Hello, Mr. Howard,
>>
>> I tried bake to vertex color,  I applied color to vertex color from
>> transparent PNG file, it took alpha properly and was showing it in 3d view.
>>
>> I then bake vertex color to PNG file, i got the transparent image.
>>
>> I think this shows that the bake color is working properly with the alpha
>> also, and don't need any modification what do you think?
>>
>> Thank you.
>>
>> On Mon, Jul 24, 2017 at 7:00 PM, Howard Trickey <howard.trickey at gmail.com
>> > wrote:
>>
>>> Hi Darshan,
>>>
>>> I will have to look more about baking to see if there is another way,
>>> but glad you found one way.
>>>
>>> Interesting about the backface culling. I was suspecting that the
>>> artifacts we were seeing were due to backfaces. But as you say, culling
>>> them is not really the best fix here. Still, a good clue.
>>>
>>> As discussed in IRC, I did the steps to the Builder to build your
>>> branch. It seemed to work.  Some builds are building now. For the record,
>>> here's what I did
>>> git checkout experimental-build
>>> git merge master
>>> git merge --squash soc-2017-vertex_paint
>>> git commit -a
>>> git revert HEAD
>>>
>>> noted that commit for the place where your code is merged in is:
>>> de3ee9f7bb
>>>
>>>
>>>
>>> On Sun, Jul 23, 2017 at 11:08 AM Darshan kadu <darsh7807 at gmail.com>
>>> wrote:
>>>
>>>> Hello, Mr, Howard,
>>>>
>>>> I had a hard time in understanding how does the bake to vertex color
>>>> works, but I figured it out.
>>>>
>>>> I did the following steps:
>>>> 1) I set the texture are the random image.
>>>> 2)Set the UV map
>>>> 3)in the physics tab get to dynamic paint tab
>>>> 4)Add canvas
>>>> 5)dynamic output: add paintmap later
>>>> 6)dynamic initial color:
>>>>    initial color: UV texture
>>>>  and then set the texture
>>>> 7) go to object modifier tab
>>>>    click apply.
>>>>
>>>> If we subdivide sufficiently we can see the image in vertex paint.
>>>> Here alpha is by default 1.
>>>> I followed these instructions: https://blender.
>>>> stackexchange.com/questions/26503/how-to-bake-uv-map-
>>>> texture-to-vertex-color-selected-to-active/41677
>>>>
>>>> I just want to know whether is this the correct way to bake or any
>>>> other method is there to bake?
>>>> This was only for texture to vertex color baking.
>>>>
>>>> Well, I enabled the backface culling in the shading panel on the
>>>> right-hand side, the alpha for subdivide was showing properly. But it
>>>> doesn't consider the back faces and for things like a plane, it's not
>>>> good(as the one side in invisible).
>>>> We can set it as default by GL functions, but it won't be correct,
>>>> right?
>>>>
>>>> Thank you.
>>>>
>>>>
>>>> On Sat, Jul 22, 2017 at 5:36 PM, Howard Trickey <
>>>> howard.trickey at gmail.com> wrote:
>>>>
>>>>> Hi Darshan,
>>>>>
>>>>> The channel locks seem to work. Thanks.
>>>>>
>>>>> I think bake color is a great next step.
>>>>>
>>>>> On Sat, Jul 22, 2017 at 7:03 AM Darshan kadu <darsh7807 at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hello, Mr. Howard,
>>>>>>
>>>>>> I have implemented the color lock and the alpha blend, have a look at
>>>>>> it I have pushed the code.
>>>>>>
>>>>>> I am now planning to work on bake color. What do you think?
>>>>>>
>>>>>> Thank you.
>>>>>>
>>>>>> On Thu, Jul 20, 2017 at 6:15 PM, Howard Trickey <
>>>>>> howard.trickey at gmail.com> wrote:
>>>>>>
>>>>>>> Hi Darshan,
>>>>>>>
>>>>>>> Your plan to next work blending alpha according to mode, and locking
>>>>>>> color, seems good to me.
>>>>>>>
>>>>>>> Somehow I don't think depth ordering is the issue with the
>>>>>>> transparent display.  We'll have to leave this as a background task to fix
>>>>>>> while moving on to other things now.  This is only meant at the moment as a
>>>>>>> kind of quick hack so the user can see some effect of changing alpha in
>>>>>>> Vertex Paint mode, and that much is accomplished.
>>>>>>>
>>>>>>> The concept of padding is that each C data type takes a certain
>>>>>>> number of bytes and is (by default, and by most compilers) aligned on
>>>>>>> certain "address boundaries" because machines access them better that way.
>>>>>>> On typical machines today:
>>>>>>> char, bool - take 1 byte, can go at any address
>>>>>>> short - takes 2 bytes, goes on even addresses
>>>>>>> int, long, float, pointer - take 4 bytes, go on multiple-of-4
>>>>>>> addresses
>>>>>>> double - takes 8 bytes, goes on multiple-of-8 addresses
>>>>>>>
>>>>>>> So when you declare a struct, it puts them in order but if the next
>>>>>>> address available would not fit the above rules, internal padding
>>>>>>> (basically, unused bytes) is inserted in order to make the required
>>>>>>> alignment. For more information, read, say https://en.wikipedia.org/
>>>>>>> wiki/Data_structure_alignment
>>>>>>>
>>>>>>> With some structs in Blender that are to be persisted to disk, we
>>>>>>> want the total length of the struct to have size that is a multiple of 8.
>>>>>>> If by following the above rules, you end up with a struct that is not a
>>>>>>> multiple of 8, you may have to add declaration of some chars and possibly
>>>>>>> an int in order to end up with a multiple of 8. Also, it seems that we
>>>>>>> explicitly put in pad declarations rather than relying on the compiler to
>>>>>>> do it for 'jumps' caused by alignment concerns. I guess this is to make it
>>>>>>> easy for a program to do size calculations when looking at the struct defs
>>>>>>> in the makesdna directory.  E.g., see the ID and PreviewImage struct defs
>>>>>>> in makesdna/DNA_ID.h for both types of pads.
>>>>>>>
>>>>>>> On Thu, Jul 20, 2017 at 6:07 AM Darshan kadu <darsh7807 at gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hello, Mr. Howard,
>>>>>>>>
>>>>>>>> Yes, I also think that the alpha should be blend similar to rgb. It
>>>>>>>> will be simple to implement.
>>>>>>>>
>>>>>>>> About the channel lock, the artists want it, so having it would be
>>>>>>>> good think, I can do it with r,g,b bool in the brush struct and changing
>>>>>>>> them from  UI,  Can you tell me the concept of padding you mention before
>>>>>>>> for adding element in the structure.
>>>>>>>>
>>>>>>>> For visualization section, Can cull face be useful? but for the
>>>>>>>> cases like plane the back view will not be displayed.
>>>>>>>>
>>>>>>>> Another thing that can be done is drawing according the depth the
>>>>>>>> most depth faces first, I haven't done it before). This blog explains this
>>>>>>>> very well https://learnopengl.com/#!Advanced-OpenGL/Blending.
>>>>>>>>
>>>>>>>> But again why only some faces are behaving like that, why not all?
>>>>>>>> This is something interesting!
>>>>>>>>
>>>>>>>> Now, I will be adding the alpha blending similar to rgb, and
>>>>>>>> locking color.
>>>>>>>>
>>>>>>>> Thank you.
>>>>>>>>
>>>>>>>> On Wed, Jul 19, 2017 at 7:39 PM, Darshan kadu <darsh7807 at gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Hello, Mr. Howard,
>>>>>>>>> Sorry, I was ill from yesterday afternoon. I should haven't told
>>>>>>>>> you before but internet wasn't very good its monsoon season(heàvy rain) in
>>>>>>>>> India.
>>>>>>>>>
>>>>>>>>> Meanwhile, yesterday I changed the ply importer to take alpha into
>>>>>>>>> account. I have pushed the code. I thing the same problem comes with the
>>>>>>>>> fbx importer. I will check it. I will give reply to your mail as soon as
>>>>>>>>> possible.
>>>>>>>>>
>>>>>>>>> Sorry, I should have told you yesterday itself.
>>>>>>>>>
>>>>>>>>> Thank you.
>>>>>>>>>
>>>>>>>>> On 19-Jul-2017 6:40 PM, "Howard Trickey" <howard.trickey at gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Darshan,
>>>>>>>>>>
>>>>>>>>>> What are you working on now?
>>>>>>>>>>
>>>>>>>>>> I looked a little more at the issue of alpha display after
>>>>>>>>>> subdividing. I am pretty sure now that the alphas are set properly -- if
>>>>>>>>>> you remove all but, say, the front (subdivided) face, the display looks OK.
>>>>>>>>>> I tried changing the glBlendfunc call to:
>>>>>>>>>> glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA,
>>>>>>>>>> GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
>>>>>>>>>> which seems more correct, but it didn't make any difference.
>>>>>>>>>>
>>>>>>>>>> Maybe someone reading this with more experience with OpenGL and
>>>>>>>>>> alpha-blending has an idea?  I wonder if somehow we have to turn on drawing
>>>>>>>>>> the elements in proper z-sorted order?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On Tue, Jul 18, 2017 at 9:48 AM Howard Trickey <
>>>>>>>>>> howard.trickey at gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> Darshan,
>>>>>>>>>>>
>>>>>>>>>>> I made a little python function to dump the vertex (loop) colors
>>>>>>>>>>> on the console.  You may find this useful.  If you put this in, say, the
>>>>>>>>>>> release/scripts/startup folder then you can use the <Space>-menu to search
>>>>>>>>>>> for 'Dump Vertex Colors'.  To see which faces and vertices correspond to
>>>>>>>>>>> which dumped colors, you can start blender with --debug and then enable the
>>>>>>>>>>> 'indices' visualization box in the right-hand panel of view3d (when in Edit
>>>>>>>>>>> mode) to see the indices of the currently selected elements.
>>>>>>>>>>>
>>>>>>>>>>> I think there may be a problem with the ply exporter, discovered
>>>>>>>>>>> by using this. I made a simple plane quad and put different colors and
>>>>>>>>>>> alphas on each, and then the ply exporter seemed to have an off-by-one
>>>>>>>>>>> error in lining up colors with vertices. But I looked briefly at the code
>>>>>>>>>>> and didn't see what was wrong.
>>>>>>>>>>>
>>>>>>>>>>> I also checked the interpolation of alpha's when subdividing and
>>>>>>>>>>> agree with you that it seems to be doing approximately the right thing, so
>>>>>>>>>>> the problem is somehow in the visualization code.
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> _______________________________________________
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>>>>>>>>>> Soc-2017-dev at blender.org
>>>>>>>>>> https://lists.blender.org/mailman/listinfo/soc-2017-dev
>>>>>>>>>>
>>>>>>>>>>
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