[SOLVED] setting transparency (alpha) for spherescenenode?

[pandoragami]

Hi All,

Sorry for asking such a noobish question considering that this has probably been answered before but I did search and found very little on how to do it, including this page

http://irrlicht.sourcearchive.com/docum ... ource.html

Anyways I have this code where I create a sphere and add a texture, what I wanted to do was to create motion trails behind it as it moves along using alpha blending methods but I can't seem to change the alpha (tansparency) of the node itself. I did find this page

http://irrlicht.sourceforge.net/forum/v ... php?t=2179

Where an animated scene node is alpha blended for each frame differently, any suggestions for just a regular sphere node?

Code: Select all

scene::ISceneNode* sphere = smgr->addSphereSceneNode( radius, 32, 0, -1, core::vector3df(0, Y, 0), core::vector3df(0, 0, 0), core::vector3df(1.0f, 1.0f, 1.0f));
    sphere->setMaterialFlag(video::EMF_LIGHTING, false);
    sphere->setMaterialTexture( 0, driver->getTexture("image.bmp"));

[CuteAlien]

You can try to experiment with IMeshManipulator::setVertexColorAlpha. As each sphere-node has it's own mesh that should work.

[pandoragami]

You can try to experiment with IMeshManipulator::setVertexColorAlpha. As each sphere-node has it's own mesh that should work.

Thanks so far, I tried this

Code: Select all

scene::IMeshManipulator* mesh = smgr->getMeshManipulator();
mesh->setVertexColorAlpha(sphere, 0);

But the compiler complains that my sphere isn't an IMesh* type?

Code: Select all

error: no matching function for call to 'irr::scene::IMeshManipulator::setVertexColorAlpha(irr::scene::ISceneNode*&, int)'|

[CuteAlien]

Use sphere->getMesh() to get the mesh.

[pandoragami]

Use sphere->getMesh() to get the mesh.

Tried but got this error.

Code: Select all

 
scene::ISceneNode* sphere = smgr->addSphereSceneNode(radius, 32, 0, -1, core::vector3df(0, 0, 0), core::vector3df(0, 0, 0), core::vector3df(1.0f, 1.0f, 1.0f));
    sphere->setMaterialFlag(video::EMF_LIGHTING, false);
    sphere->setMaterialTexture( 0, driver->getTexture("graph.jpg"));
 
    scene::IMeshManipulator* mesh = smgr->getMeshManipulator();
    mesh->setVertexColorAlpha(sphere->getMesh(), 0);
 
error: 'class irr::scene::ISceneNode' has no member named 'getMesh'|

[CuteAlien]

Well, then take a look at the documentation which type addSphereSceneNode does return: http://irrlicht.sourceforge.net/docu/cl ... 63970cfc04

Maybe you are lucky and it's real type does have such a function ;-)

[pandoragami]

Well, then take a look at the documentation which type addSphereSceneNode does return: http://irrlicht.sourceforge.net/docu/cl ... 63970cfc04

Maybe you are lucky and it's real type does have such a function

It returns a type IMeshSceneNode, but how come ISceneNode works?

Anyways this compiles,

Code: Select all

scene::IMeshSceneNode* sphere = smgr->addSphereSceneNode(radius, 32, 0, -1, core::vector3df(0, 0, 0), core::vector3df(0, 0, 0), core::vector3df(1.0f, 1.0f, 1.0f));
    sphere->setMaterialFlag(video::EMF_LIGHTING, false);
    sphere->setMaterialTexture( 0, driver->getTexture("graph.jpg"));
 
    scene::IMeshManipulator* mesh = smgr->getMeshManipulator();
    mesh->setVertexColorAlpha(sphere->getMesh(), 0);

But I was expecting the sphere to vanish since the second parameter is zero in mesh->setVertexColorAlpha(sphere->getMesh(), 0)

Am I misunderstanding alpha channels? Does this not work with textured meshes?

[CuteAlien]

IMeshSceneNode is derived from ISceneNode, meaning it has everything ISceneNode has + some additional stuff. That's why you can always cast safely to the base-classes.

Not sure right now if the alpha value means transparence or opaque, doesn't seem to be documented. Just try it with 255 maybe.

[pandoragami]

IMeshSceneNode is derived from ISceneNode, meaning it has everything ISceneNode has + some additional stuff. That's why you can always cast safely to the base-classes.

Not sure right now if the alpha value means transparence or opaque, doesn't seem to be documented. Just try it with 255 maybe.

Tried both 0 and 255, no luck either way.

[pandoragami]

Here's the complete code

Code: Select all

 
#include <irrlicht.h>
 
using namespace irr;
 
class MyEventReceiver : public IEventReceiver
{
public:
 
    struct SMouseState
    {
        core::position2di Position;
        bool LeftButtonDown;
        SMouseState() : LeftButtonDown(false) { }
    } MouseState;
 
    virtual bool OnEvent(const SEvent& event)
    {
        if (event.EventType == irr::EET_KEY_INPUT_EVENT)
            KeyIsDown[event.KeyInput.Key] = event.KeyInput.PressedDown;
 
        if(event.EventType == EET_MOUSE_INPUT_EVENT)
        {
            switch(event.MouseInput.Event)
            {
            case EMIE_LMOUSE_PRESSED_DOWN:
                MouseState.LeftButtonDown = true;
                break;
 
            case EMIE_LMOUSE_LEFT_UP:
                MouseState.LeftButtonDown = false;
                break;
 
            case EMIE_MOUSE_MOVED:
                MouseState.Position.X = event.MouseInput.X;
                MouseState.Position.Y = event.MouseInput.Y;
                break;
 
            default:
 
                break;
            }
        }
 
        return false;
    }
 
    // This is used to check whether a key is being held down
    virtual bool IsKeyDown(EKEY_CODE keyCode) const
    {
        return KeyIsDown[keyCode];
    }
 
    const SMouseState & GetMouseState(void) const
    {
        return MouseState;
    }
 
    MyEventReceiver()
    {
        for (u32 i=0; i<KEY_KEY_CODES_COUNT; ++i)
            KeyIsDown[i] = false;
    }
 
private:
    // We use this array to store the current state of each key
    bool KeyIsDown[KEY_KEY_CODES_COUNT];
};
 
MyEventReceiver receiver;
IrrlichtDevice* device = 0;
const int SCRX = 640;
const int SCRY = 480;
const float radius = 5.0f;
 
int main()
{
    device = createDevice( irr::video::EDT_OPENGL, core::dimension2d<u32>( SCRX, SCRY), 16, false, false, false, &receiver);
 
    if (device == 0)
        return 1;
 
    video::IVideoDriver* driver = device->getVideoDriver();
    scene::ISceneManager* smgr = device->getSceneManager();
 
    driver->setTextureCreationFlag(video::ETCF_CREATE_MIP_MAPS, true);
 
    scene::ICameraSceneNode* cam = smgr->addCameraSceneNodeFPS( 0, 50.0f, 0.01f, -1, 0, 0, false, 0.0f, false, true);
 
    device->getCursorControl()->setVisible(false);
    scene::IMeshSceneNode* sphere = smgr->addSphereSceneNode(radius, 32, 0, -1, core::vector3df(0, 0, 0), core::vector3df(0, 0, 0), core::vector3df(1.0f, 1.0f, 1.0f));
    sphere->setMaterialFlag(video::EMF_LIGHTING, false);
    sphere->setMaterialTexture( 0, driver->getTexture("graph.jpg"));
 
    scene::IMeshManipulator* mesh = smgr->getMeshManipulator();
    mesh->setVertexColorAlpha(sphere->getMesh(), 255);
 
    cam->setPosition( core::vector3df( 0, 0,-15));
    cam->setTarget( core::vector3df( 0.0f, 0.0f, 0.0f));
 
    int lastFPS = -1;
 
 
    while(device->run())
    if (device->isWindowActive())
    {
        driver->beginScene(true, true, video::SColor( 255, 0, 0, 0));
        smgr->drawAll();
        driver->endScene();
 
        int fps = driver->getFPS();
 
        if (lastFPS != fps)
        {
            core::stringw str = L"Irrlicht Text Node [";
            str += driver->getName();
            str += "] FPS:";
            str += fps;
 
            device->setWindowCaption(str.c_str());
            lastFPS = fps;
        }
 
        device->sleep(50);
    }
 
    device->drop();
 
    return 0;
}

[CuteAlien]

Hm, I really have to sleep, so won't test now. But I suppose it's because the material used in the mesh is solid. Try using any material supporting transparence like video::EMT_TRANSPARENT_ADD_COLOR.

[pandoragami]

Hm, I really have to sleep, so won't test now. But I suppose it's because the material used in the mesh is solid. Try using any material supporting transparence like video::EMT_TRANSPARENT_ADD_COLOR.

Goodnite, thanks so far though, this code below works now except that the texture cannot be alpha blended so it's commented out.

Code: Select all

 
#include <C:\irrlicht-1.7.2\include\irrlicht.h>
 
using namespace irr;
 
class MyEventReceiver : public IEventReceiver
{
public:
 
    struct SMouseState
    {
        core::position2di Position;
        bool LeftButtonDown;
        SMouseState() : LeftButtonDown(false) { }
    } MouseState;
 
    virtual bool OnEvent(const SEvent& event)
    {
        if (event.EventType == irr::EET_KEY_INPUT_EVENT)
            KeyIsDown[event.KeyInput.Key] = event.KeyInput.PressedDown;
 
        if(event.EventType == EET_MOUSE_INPUT_EVENT)
        {
            switch(event.MouseInput.Event)
            {
            case EMIE_LMOUSE_PRESSED_DOWN:
                MouseState.LeftButtonDown = true;
                break;
 
            case EMIE_LMOUSE_LEFT_UP:
                MouseState.LeftButtonDown = false;
                break;
 
            case EMIE_MOUSE_MOVED:
                MouseState.Position.X = event.MouseInput.X;
                MouseState.Position.Y = event.MouseInput.Y;
                break;
 
            default:
 
                break;
            }
        }
 
        return false;
    }
 
    // This is used to check whether a key is being held down
    virtual bool IsKeyDown(EKEY_CODE keyCode) const
    {
        return KeyIsDown[keyCode];
    }
 
    const SMouseState & GetMouseState(void) const
    {
        return MouseState;
    }
 
    MyEventReceiver()
    {
        for (u32 i=0; i<KEY_KEY_CODES_COUNT; ++i)
            KeyIsDown[i] = false;
    }
 
private:
    // We use this array to store the current state of each key
    bool KeyIsDown[KEY_KEY_CODES_COUNT];
};
 
MyEventReceiver receiver;
IrrlichtDevice* device = 0;
const int SCRX = 640;
const int SCRY = 480;
const float radius = 5.0f;
 
int main()
{
    device = createDevice( irr::video::EDT_OPENGL, core::dimension2d<u32>( SCRX, SCRY), 16, false, false, false, &receiver);
 
    if (device == 0)
        return 1;
 
    video::IVideoDriver* driver = device->getVideoDriver();
    scene::ISceneManager* smgr = device->getSceneManager();
 
    driver->setTextureCreationFlag(video::ETCF_CREATE_MIP_MAPS, true);
 
    scene::ICameraSceneNode* cam = smgr->addCameraSceneNodeFPS( 0, 50.0f, 0.01f, -1, 0, 0, false, 0.0f, false, true);
 
    device->getCursorControl()->setVisible(false);
    scene::IMeshSceneNode* sphere = smgr->addSphereSceneNode(radius, 32, 0, -1, core::vector3df(0, 0, 0), core::vector3df(0, 0, 0), core::vector3df(1.0f, 1.0f, 1.0f));
    sphere->setMaterialFlag(video::EMF_LIGHTING, false);
    //sphere->setMaterialTexture( 0, driver->getTexture("graph.jpg"));
    sphere->setMaterialType(video::EMT_TRANSPARENT_ALPHA_CHANNEL);
 
    scene::IMeshManipulator* mesh = smgr->getMeshManipulator();
    mesh->setVertexColorAlpha(sphere->getMesh(), 155);
 
 
    cam->setPosition( core::vector3df( 0, 0,-15));
    cam->setTarget( core::vector3df( 0.0f, 0.0f, 0.0f));
 
    int lastFPS = -1;
 
    while(device->run())
    if (device->isWindowActive())
    {
        driver->beginScene(true, true, video::SColor( 255, 0, 0, 0));
        smgr->drawAll();
        driver->endScene();
 
        int fps = driver->getFPS();
 
        if (lastFPS != fps)
        {
            core::stringw str = L"Irrlicht Text Node [";
            str += driver->getName();
            str += "] FPS:";
            str += fps;
 
            device->setWindowCaption(str.c_str());
            lastFPS = fps;
        }
 
        device->sleep(50);
    }
 
    device->drop();
 
    return 0;
}
 
 
 
 

[thanhle]

There's a post by an author call feelthat.
I saw a few weeks back, he did transparent even for animated mesh.
I think he fixed other issues he found as well.


Actually there's also lot of posts on the related issue if you search the forum.

http://irrlicht.sourceforge.net/forum/v ... hp?t=31400

Regards
thanh

[pandoragami]

There's a post by an author call feelthat.
I saw a few weeks back, he did transparent even for animated mesh.
I think he fixed other issues he found as well.


Actually there's also lot of posts on the related issue if you search the forum.

http://irrlicht.sourceforge.net/forum/v ... hp?t=31400

Regards
thanh

Thanks for the note, I did check his code and he is using "EMT_TRANSPARENT_ALPHA_CHANNEL" just like me in the following code below, but I set the alpha to zero and still the texture doesn't allow it to be transparent? I've tried other enumerators too, if you look you'll notice several, here's all of them

Code: Select all

video::EMT_TRANSPARENT_ALPHA_CHANNEL
    video::EMT_TRANSPARENT_ALPHA_CHANNEL_REF
    video::EMT_TRANSPARENT_VERTEX_ALPHA
    video::EMT_TRANSPARENT_ALPHA_CHANNEL

Code: Select all

 
#include <irrlicht.h>
 
using namespace irr;
 
class MyEventReceiver : public IEventReceiver
{
public:
 
    struct SMouseState
    {
        core::position2di Position;
        bool LeftButtonDown;
        SMouseState() : LeftButtonDown(false) { }
    } MouseState;
 
    virtual bool OnEvent(const SEvent& event)
    {
        if (event.EventType == irr::EET_KEY_INPUT_EVENT)
            KeyIsDown[event.KeyInput.Key] = event.KeyInput.PressedDown;
 
        if(event.EventType == EET_MOUSE_INPUT_EVENT)
        {
            switch(event.MouseInput.Event)
            {
            case EMIE_LMOUSE_PRESSED_DOWN:
                MouseState.LeftButtonDown = true;
                break;
 
            case EMIE_LMOUSE_LEFT_UP:
                MouseState.LeftButtonDown = false;
                break;
 
            case EMIE_MOUSE_MOVED:
                MouseState.Position.X = event.MouseInput.X;
                MouseState.Position.Y = event.MouseInput.Y;
                break;
 
            default:
 
                break;
            }
        }
 
        return false;
    }
 
    // This is used to check whether a key is being held down
    virtual bool IsKeyDown(EKEY_CODE keyCode) const
    {
        return KeyIsDown[keyCode];
    }
 
    const SMouseState & GetMouseState(void) const
    {
        return MouseState;
    }
 
    MyEventReceiver()
    {
        for (u32 i=0; i<KEY_KEY_CODES_COUNT; ++i)
            KeyIsDown[i] = false;
    }
 
private:
    // We use this array to store the current state of each key
    bool KeyIsDown[KEY_KEY_CODES_COUNT];
};
 
MyEventReceiver receiver;
IrrlichtDevice* device = 0;
const int SCRX = 640;
const int SCRY = 480;
const float radius = 5.0f;
 
int main()
{
    device = createDevice( irr::video::EDT_OPENGL, core::dimension2d<u32>( SCRX, SCRY), 16, false, false, false, &receiver);
 
    if (device == 0)
        return 1;
 
    video::IVideoDriver* driver = device->getVideoDriver();
    scene::ISceneManager* smgr = device->getSceneManager();
 
    driver->setTextureCreationFlag(video::ETCF_CREATE_MIP_MAPS, true);
 
    scene::ICameraSceneNode* cam = smgr->addCameraSceneNodeFPS( 0, 50.0f, 0.01f, -1, 0, 0, false, 0.0f, false, true);
 
    device->getCursorControl()->setVisible(false);
    scene::IMeshSceneNode* sphere = smgr->addSphereSceneNode(radius, 32, 0, -1, core::vector3df(0, 0, 0), core::vector3df(0, 0, 0), core::vector3df(1.0f, 1.0f, 1.0f));
    sphere->setMaterialFlag(video::EMF_LIGHTING, false);
    sphere->setMaterialTexture( 0, driver->getTexture("graph.jpg"));
    //sphere->setMaterialType(video::EMT_TRANSPARENT_ALPHA_CHANNEL);
    //sphere->setMaterialType(video::EMT_TRANSPARENT_ALPHA_CHANNEL_REF);
    //sphere->setMaterialType(video::EMT_TRANSPARENT_VERTEX_ALPHA);
    sphere->setMaterialType(video::EMT_TRANSPARENT_ALPHA_CHANNEL);
    scene::IMeshManipulator* mesh = smgr->getMeshManipulator();
    mesh->setVertexColorAlpha(sphere->getMesh(), 0);
 
 
    cam->setPosition( core::vector3df( 0, 0,-15));
    cam->setTarget( core::vector3df( 0.0f, 0.0f, 0.0f));
 
    int lastFPS = -1;
 
    while(device->run())
    if (device->isWindowActive())
    {
        driver->beginScene(true, true, video::SColor( 255, 0, 0, 0));
        smgr->drawAll();
        driver->endScene();
 
        int fps = driver->getFPS();
 
        if (lastFPS != fps)
        {
            core::stringw str = L"Irrlicht Text Node [";
            str += driver->getName();
            str += "] FPS:";
            str += fps;
 
            device->setWindowCaption(str.c_str());
            lastFPS = fps;
        }
 
        device->sleep(50);
    }
 
    device->drop();
 
    return 0;
}
 
 
 
 

[mongoose7]

Code: Select all

Meshbuffer->Material.DiffuseColor.setAlpha( (s32)(value * 255) );
Meshbuffer->Material.MaterialType = video::EMT_TRANSPARENT_VERTEX_ALPHA;