I'm trying to use assimp to load models in a program.  I see the Derelict binding is for version 3.3, but the assimp site has no binaries for this, just source.  So I try to use version 3.1.1 and I get this error:

derelict.util.exception.SymbolLoadException@..\..\AppData\Roaming\dub\packages\derelict-util-2.0.6\derelict-util\source\derelict\util\exception.d(35): Failed to load symbol aiReleaseExportFormatDescription from shared library assimp.dll

Is this a version problem that I need 3.3 for?  If so, I don't know how to build the .dll since I'm still new to programming.  Please send help!  :)

On Monday, 9 January 2017 at 18:13:03 UTC, Dlearner wrote:
> I'm trying to use assimp to load models in a program.  I see the Derelict binding is for version 3.3, but the assimp site has no binaries for this, just source.  So I try to use version 3.1.1 and I get this error:
>
> derelict.util.exception.SymbolLoadException@..\..\AppData\Roaming\dub\packages\derelict-util-2.0.6\derelict-util\source\derelict\util\exception.d(35): Failed to load symbol aiReleaseExportFormatDescription from shared library assimp.dll

Use version 1.1.1 of DerelictASSIMP3. It's implemented against ASSIMP 3.1.

On Tuesday, 10 January 2017 at 00:10:12 UTC, Mike Parker wrote:
> On Monday, 9 January 2017 at 18:13:03 UTC, Dlearner wrote:
>> I'm trying to use assimp to load models in a program.  I see the Derelict binding is for version 3.3, but the assimp site has no binaries for this, just source.  So I try to use version 3.1.1 and I get this error:
>>
>> derelict.util.exception.SymbolLoadException@..\..\AppData\Roaming\dub\packages\derelict-util-2.0.6\derelict-util\source\derelict\util\exception.d(35): Failed to load symbol aiReleaseExportFormatDescription from shared library assimp.dll
>
> Use version 1.1.1 of DerelictASSIMP3. It's implemented against ASSIMP 3.1.

A-haa, thank you!

Need to rez this thread because I ran into a wall.  Two little things:

1) Can't seem to get the Importer class to work ("undefined identifier 'Importer' ", etc), and
2) GetTexture and GetTextureCount for aiMaterial don't seem to work
(source\model.d(105,28): Error: no property 'GetTextureCount' for type 'aiMaterial*'
source\model.d(107,6): Error: no property 'GetTexture' for type 'aiMaterial*')

There are some const issues, too, but I can hack around them.  Does anyone have any experience with these?

I came back to this project and realised my mistakes (Importer is a class for the C++ API, and we're using the C API).
So I fixed all my errors, but now I get an access violation.
As far as I can tell, it seems to be an issue with `aiGetMaterialTexture`.  It is meant to return an aiString with a filename (default value of "$texture.png"), I believe.  But I get:

aiString(13, x"67 6C 61 73 73 5F 64 69 66 2E 70 6E 67 00 FF FF FF ... FF"c)
[shortened for brevity]

I'm meant to add this on to a directory string so I can load an image, but obviously this wouldn't work.

I thought it might be a problem with converting from D-strings to C-strings.  I sent a string to `aiImportFile` as `toStringz(path)`.
I tested this with some writeln debugging:

```
auto temp = path.toStringz;
writeln("toStringz: ", temp);
writeln("string: ", temp.to!string);
```

This gave:
toStringz: 4770B6
string: Models/Nanosuit/nanosuit.obj

So maybe this is a problem with using aiStrings?  I'm quite confused.  Sorry if this is more of an assimp question than a D question, but I don't know if it's me misusing D language features or not.

On Sunday, 26 March 2017 at 10:34:21 UTC, Dlearner wrote:
> I came back to this project and realised my mistakes (Importer is a class for the C++ API, and we're using the C API).
> So I fixed all my errors, but now I get an access violation.
> As far as I can tell, it seems to be an issue with `aiGetMaterialTexture`.  It is meant to return an aiString with a filename (default value of "$texture.png"), I believe.  But I get:
>
> aiString(13, x"67 6C 61 73 73 5F 64 69 66 2E 70 6E 67 00 FF FF FF ... FF"c)
> [shortened for brevity]

The data is "glass_dif.png", followed by a null terminator, followed by a bunch of 0xFFs. 13 is the length of "glass_dif.png". Judging from the definition of aiString [1], the 0xFFs are just unused space. So, this looks good.

> I'm meant to add this on to a directory string so I can load an image, but obviously this wouldn't work.

To convert an aiString to a D string, it should be possible to slice the data with the length:

    aiString x;
    const(char)[] y = x.data[0 .. x.length];

You have to be cautiots of lifetime requirements, of course. If needed, you can make a copy with dup (mutable copy) or idup (immutable copy):

    const(char)[] y = x.data[0 .. x.length].dup;
    string z = x.data[0 .. x.length].idup;


[1] http://www.assimp.org/lib_html/structai_string.html

On Sunday, 26 March 2017 at 11:10:55 UTC, ag0aep6g wrote:
> On Sunday, 26 March 2017 at 10:34:21 UTC, Dlearner wrote:
>> I came back to this project and realised my mistakes (Importer is a class for the C++ API, and we're using the C API).
>> So I fixed all my errors, but now I get an access violation.
>> As far as I can tell, it seems to be an issue with `aiGetMaterialTexture`.  It is meant to return an aiString with a filename (default value of "$texture.png"), I believe.  But I get:
>>
>> aiString(13, x"67 6C 61 73 73 5F 64 69 66 2E 70 6E 67 00 FF FF FF ... FF"c)
>> [shortened for brevity]
>
> The data is "glass_dif.png", followed by a null terminator, followed by a bunch of 0xFFs. 13 is the length of "glass_dif.png". Judging from the definition of aiString [1], the 0xFFs are just unused space. So, this looks good.
>
>> I'm meant to add this on to a directory string so I can load an image, but obviously this wouldn't work.
>
> To convert an aiString to a D string, it should be possible to slice the data with the length:
>
>     aiString x;
>     const(char)[] y = x.data[0 .. x.length];
>
> You have to be cautiots of lifetime requirements, of course. If needed, you can make a copy with dup (mutable copy) or idup (immutable copy):
>
>     const(char)[] y = x.data[0 .. x.length].dup;
>     string z = x.data[0 .. x.length].idup;
>
>
> [1] http://www.assimp.org/lib_html/structai_string.html

Ahh this did help!  I practically followed your advice, then fixed a somewhat unrelated range violation, and got a similar "object.Error@(0): Access Violation".  But in the console I got:
filename: Models/Nanosuit/glass_dif.png
filename: Models/Nanosuit/leg_dif.png
filename: Models/Nanosuit/leg_showroom_spec.png
filename: Models/Nanosuit/hand_dif.png
filename: Models/Nanosuit/hand_showroom_spec.png
filename: Models/Nanosuit/arm_dif.png
filename: Models/Nanosuit/arm_showroom_spec.png
filename: Models/Nanosuit/helmet_diff.png

About half the textures seem to load fine.  Some progress!

On Sunday, 26 March 2017 at 12:40:42 UTC, Dlearner wrote:

> ...
> About half the textures seem to load fine.  Some progress!

I don't know why, but when I get to the 8th texture, the filename has some garbage attached.

SDL_Surface* surface = IMG_Load(filename.ptr);
    if (surface is null) {
        writeln("surface is null: ", to!string(IMG_GetError()));
    } else {
        writeln(filename);
    }

From console:
surface is null: Couldn't open Models/Nanosuit/helmet_diff.pngÇ2ÿ

I'm assuming the previous textures didn't experience this, but I have no idea what could be the problem here, especially as the filename seems fine when I writeln it.
:(

On 03/26/2017 11:31 PM, Dlearner wrote:
> SDL_Surface* surface = IMG_Load(filename.ptr);
>     if (surface is null) {
>         writeln("surface is null: ", to!string(IMG_GetError()));
>     } else {
>         writeln(filename);
>     }
>
> From console:
> surface is null: Couldn't open Models/Nanosuit/helmet_diff.pngÇ2ÿ
>
> I'm assuming the previous textures didn't experience this, but I have no
> idea what could be the problem here, especially as the filename seems
> fine when I writeln it.
> :(

How do you construct `filename`? Looks like it's not properly null-terminated.

If you followed my (short-sighted) `dup` advice, that doesn't do null-termination. Since the original strings are null-terminated, just slicing one more character should do the trick. I'd put an assert that verifies that the last character is '\0'.

I.e.:
----
string z = x.data[0 .. x.length + 1].idup;
assert(z[$ - 1] == '\0');
----

Generally, don't pass just the pointer of a string unless you know for sure that it's properly null-terminated.

If you're using a slice directly, without `dup`-ing, then the original aiString would seem to be broken already.

On Sunday, 26 March 2017 at 21:52:42 UTC, ag0aep6g wrote:
> On 03/26/2017 11:31 PM, Dlearner wrote:
>> SDL_Surface* surface = IMG_Load(filename.ptr);
>>     if (surface is null) {
>>         writeln("surface is null: ", to!string(IMG_GetError()));
>>     } else {
>>         writeln(filename);
>>     }
>>
>> From console:
>> surface is null: Couldn't open Models/Nanosuit/helmet_diff.pngÇ2ÿ
>>
>> I'm assuming the previous textures didn't experience this, but I have no
>> idea what could be the problem here, especially as the filename seems
>> fine when I writeln it.
>> :(
>
> How do you construct `filename`? Looks like it's not properly null-terminated.
>
> If you followed my (short-sighted) `dup` advice, that doesn't do null-termination. Since the original strings are null-terminated, just slicing one more character should do the trick. I'd put an assert that verifies that the last character is '\0'.
>
> I.e.:
> ----
> string z = x.data[0 .. x.length + 1].idup;
> assert(z[$ - 1] == '\0');
> ----
>
> Generally, don't pass just the pointer of a string unless you know for sure that it's properly null-terminated.
>
> If you're using a slice directly, without `dup`-ing, then the original aiString would seem to be broken already.

Ahh you were absolutely right.  I concatenated a '\0' and it worked.  Silly me!
Most of the textures loaded and a really broken model appears, but I'm guessing that's a result of trying to follow along with a tutorial written for C++ in D.
Thank you for your help.  I really appreciate it.  :)