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

Howard Trickey howard.trickey at gmail.com
Tue Jul 25 13:54:32 CEST 2017 

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.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> Soc-2017-dev mailing list
>>>>>>>>> Soc-2017-dev at blender.org
>>>>>>>>> https://lists.blender.org/mailman/listinfo/soc-2017-dev
>>>>>>>>>
>>>>>>>>>
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>>>>>>>
>>>>>>
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>>>>>>
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>>>>
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