Complex object in 3d opengl Android - android

I am given a task of making some complex 3d object in opengl android.Earlier I have worked only on the primitive objects of opengl using nehe tutorials.
I have googled and found that Blender is used to make 3d object and then it is imported in android project .But I cant get HOW?


One easy way to do it is to export your objects in the OBJ format (it describes vertices of an object). You can then easily make your own OBJ reader (or use an existing one) and pass the vertices to OpenGL.
Else, don't reinvent the wheel and use a library that already does this for you (libgdx for instance).


... then it
is imported in android project
Actually it's usually not imported but simply load from file by the target application. There are some export scripts for Blender that emit C code or even write out OpenGL calls; DON'T use them, they'll just mess up your program.
There are some good libraries for 3D object storage, like OpenCTM


What you need is an array of floats that represent your vertices/normals, like so:
float [ ] vertices = {
VertexX, VertexY, VertexZ, NormalX, NormalY, NormalZ,
VertexX, VertexY, VertexZ, NormalX, NormalY, NormalZ,
VertexX, VertexY, VertexZ, NormalX, NormalY, NormalZ,
VertexX, VertexY, VertexZ, NormalX, NormalY, NormalZ,
..., ..., ..., ..., ..., ...,
};
Where each face has three unique vertex lines associated with it. Once you have this array built from an OBJ file or whatever format you want, using code that you'll have to figure out, you can render it by doing the following:
glVertexPointer(3, GL_FLOAT, sizeof(vertices[0])*6, &vertices[0]);
glNormalPoitner(GL_FLOAT, sizeof(vertices[0])*6, &vertices[3]);
glDrawArrays(GL_TRIANGLES, 0, numVertices);
See this Wikipedia page on the OBJ format for reference on how the obj file is laid out. Parsing the file is pretty straightforward once you understand the format.

Related

Tensorflow Lite Object Detection with Custom AutoML Model

I like to test the Object Detection Example of TFLite.
https://github.com/tensorflow/examples/tree/master/lite/examples/object_detection/android
The example with the default Model works great. But I want to test a custom Model generated from AutoML. When I am replace the "detect.tflite" and "labelmap fille" in the "\src\main\assets" directory and build then the App crashes after launch.
My Model is very simple ... can detect only 2 objects (Tiger and Lion). And my labelmap file contains below:
???
Tiger
Lion
Also I comment the line "//apply from:'download_model.gradle'" in "build.gradle" to stop the download of default Model and use my custom Model from asset.
I new in both Android and this ML space. I'll be glad if anyone can advise for App crash after launch with custom AutoML Model.
Thanks in advance.
Regards.

Two probable errors on log might be:
Cannot convert between a TensorFlowLite buffer with 1080000 bytes and a ByteBuffer with 270000 bytes. Modify TF_OD_API_INPUT_SIZE accordingly.
tflite ml google [1, 20, 4] and a Java object with shape [1, 10, 4]. Modify NUM_DETECTIONS according to custom model.

Import Wavefront .obj model to ARCore OpenGL project

I'm trying out the java_arcore_hello_ar sample app but replacing the andy.obj with my own model created in Blender. I have exported the blender object using settings from this tutorial
The .obj and .mtl files were placed in the assets folder but when I tap on the screen I get nothing. It doesn't show an error so I'm thinking it does place the object on the screen but is not drawing it for whatever reason.
Any Google searching for results generally bring up tutorials where you have to create a parser for converting the object, but as far as I can see, the ObjectRenderer class in arcore package does this heavy lifting for you.
Has anyone tried this with any success? Do I have to do further work with the .mtl file?

I did get this worked by extending the code to reade OBJ and MTL files.
You can take a look at my code # https://github.com/JohnLXiang/arcore-sandbox .
I'm also new to openGL, my code is not perfect but works at least.

If it does't any error information , I think the reasons are:
1.The Obj model has been placed other position , for example far far place . So you should check if model's position is origin of Blender in modeling process .
2.The Obj model is different one of java_arcore_hello_ar sample , so when java_arcore_hello_ar sample's Obj parse library parsed error.
So, you can parse obj model by yourself.

Can't load 3ds Model with multiple texture files using Rajawali for android

I am loading a 3ds model using Rajawali for android and its displaying correctly.
parser = new Loader3DSMax(this, R.raw.riale_3ds);
But the object has multiple Texture jpgs provided with it. I cant figure out how to use those Textures together in Rajawali. I have seen the object opens correctly in other 3d model viewers on my PC.
material.addTexture(new Texture("dcmap1", R.drawable.dcmap1));
material.addTexture(new Texture("dcmap2", R.drawable.dcmap2));
material.addTexture(new Texture("dcmap3", R.drawable.dcmap3));
I am applying this material on the object, if I apply only one it seems ok but when I do something as above it messes up.

Drawing text (open gl es, android)

I'm new to open gl in android and I need to draw some text in my GLSurfaceView. I found only one solution - to create bitmap with text and display it like texture (like this, for example; http://giantandroid.blogspot.ru/2011/03/draw-text-in-opengl-es.html). I tried to do like this, but it didn't work for me. What is textures array in this code? And is there any simplier way to display text?

openGL by itself doesn't offer any "simpler" way to render text - it even doesn't "know" anything about the way glyphs may be represented in bitmap or outline font sets.
Using some other library "knowing" how to handle different font sets and how to rasterize them to directly let them paint into an openGL texture doesn't seem so complicated that any other approach may claim to be a lot easier.
You might want to take a look at both this (see: Draw text in OpenGL ES) article here on stackoverflow as well as into the linked pages to get an overview of other methods available to choose the one that seems best to you.
Regarding your second question about the textures array in the code sample you linked the array is just used to fulfill the API requirements of the call to glGenTextures() as it expects an array as the second argument.
In fact just a single texture id is allocated in this line:
gl.glGenTextures(1, textures, 0);
Taking a look at the spec (see: http://docs.oracle.com/javame/config/cldc/opt-pkgs/api/jb/jsr239/javax/microedition/khronos/opengles/GL10.html) it turns out there is just a single texture id allocated stored at index 0 in the textures array.
Why then a (pseudo) array at all?
The seemingly complex signature of the java method
public void glGenTextures(int n, int[] textures, int offset)
is due to the fact that there are no pointers in java while the C function that gets wrappped requires a pointer as it's second argument:
void glGenTextures(GLsizei n, GLuint *textures);
As in C code allocating a single texture can be done with:
GLuint texture_id;
glGenTextures (1, &texture_id);
there is no need for a special function just returning a single texture id, so there's only a single glGenTextures() function available.
To allow for allocations that can be done with pointer arithmetic like:
GLuint textures[10];
glGenTextures (3, textures + 5);
in C the java wrapper allows for a third parameter specifying the starting index from which to assign allocated texture ids.
The corresponding method invocation in java would look like this:
int[] textures = new int[10];
glGenTextures (3, textures, 5);
Thus one more parameter in java wrapper and the requirement to use an array even if only a single id is needed.

Is there a way to import a 3D model into Android?

Is it possible to create a simple 3D model (for example in 3DS MAX) and then import it to Android?

That's where I got to:
I've used Google's APIDemos as a starting point - there are rotating cubes in there, each specified by two arrays: vertices and indices.
I've build my model using Blender and exported it as OFF file - it's a text file that lists all the vertices and then faces in terms of these vertices (indexed geometry)
Then I've created a simple C++ app that takes that OFF and writes it as two XMLs containing arrays (one for vertices and one for indices)
These XML files are then copied to res/values and this way I can assign the data they contain to arrays like this:
int vertices[] = context.getResources().getIntArray(R.array.vertices);
I also need to manually change the number of faces to be drawn in here: gl.glDrawElements(GL10.GL_TRIANGLES, 212*6, GL10.GL_UNSIGNED_SHORT, mIndexBuffer); - you can find that number (212 in this case) on top of the OFF file
Here you can find my project page, which uses this solution: Github project > vsiogap3d

you may export it to ASE format.
from ASE, you can convert it to your code manually or programatically.
You will need vertex for vertices array and faces for indices in Android.
don't forget you have to set
gl.glFrontFace(GL10.GL_CCW);
because 3ds max default is counter clockwise.

It should be possible. You can have the file as a data file with your program (and as such it will be pushed onto the emulator and packaged for installation onto an actual device). Then you can write a model loader and viewer in java using the Android and GLES libraries to display the model.
Specific resources on this are probably limited though. 3ds is a proprietry format so 3rd party loaders are in shortish supply and mostly reverse engineered. Other formats (such as blender or milkshape) are more open and you should be able to find details on writing a loader for them in java fairly easily.

Have you tried min3d for android? It supports 3ds max,obj and md2 models.

Not sure about Android specifically, but generally speaking you need a script in 3DS Max that manually writes out the formatting you need from the model.
As to whether one exists for Android or not, I do not know.

You can also convert 3DS MAX model with the 3D Object Converter
http://web.t-online.hu/karpo/
This tool can convert 3ds object to text\xml format or c code.
Please note that the tool is not free. You can try for a 30-day trial period. 'C' code and XML converters are available.
'c' OpenGL output example:
glDisable(GL_TEXTURE_2D);
glEnable(GL_LIGHTING);
glEnable(GL_NORMALIZE);
GLfloat Material_1[] = { 0.498039f, 0.498039f, 0.498039f, 1.000000f };
glBegin(GL_TRIANGLES);
glMaterialfv(GL_FRONT,GL_DIFFUSE,Material_1
glNormal3d(0.452267,0.000000,0.891883);
glVertex3d(5.108326,1.737655,2.650969);
glVertex3d(9.124107,-0.002484,0.614596);
glVertex3d(9.124107,4.039649,0.614596);
glEnd();
Or direct 'c' output:
Point3 Object1_vertex[] = {
{5.108326,1.737655,2.650969},
{9.124107,-0.002484,0.614596},
{9.124107,4.039649,0.614596}};
long Object1_face[] = {
3,0,1,2,
3,3,4,5
3,6,3,5};
You can migrate than those collections of objects to your Java code.

Categories

Resources