[fixed]OpenGL draw2DLine sometimes draws 2-pixel-thick line

[squisher]

Hi,

I'm not sure what causes it unfortunately, but sometimes the GL state is messed up so 1-pixel lines are drawn as 2-pixels.

The problem can only occur with 255 alpha.

COpenGLDriver::draw2DLine calls setRenderStates2DMode(color.getAlpha() < 255, false, false);

If the first parameter (alpha) is true, the problem does not occur.

If it is false, then the problem can *sometimes* occur.

Sorry I can't provide an example to replicate it... drawing the line with 254 alpha is an acceptable workaround for now...

[hybrid]

This might be caused by the anti-aliasing. Although this should be disabled for 2d drawings. Can you provide an example which reproduces this?

[vins]

I have had similar problems. When I have antialiasing disabled in device creation parameters lines are drawn like with 2 pixels. I have to disable antialiasing to each material manually to fix this. When antialiasing is enabled in device creation everything looks ok. Interesting it is that if I disable the antialiasing only to one of the materials - it desn't make any effect. I have to disable antialiasing to all nodes. I'll try to create an example today or tomorrow to reproduce this.

[hybrid]

Ah, could be that the line anti-aliasing (which does not require the multisampling of the device) is not properly disabled and state checked. Maybe your gfx card does handle lina anti-aliasing also different when multi-sampling is enabled, which could explain the better results when the device has AA enabled. I'll try to check all state changes, but the example would still help a lot.

[vins]

By the way I'm talking about 3D lines. Now I saw that it's about draw2DLine. I'll try to create an example late tonight when I get home from work.

[vins]

Ok. I had free time so I made an example. Very simple one.

Code: Select all

#include <irrlicht.h>

using namespace irr;
using namespace core;
using namespace scene;
using namespace video;
using namespace io;
using namespace gui;


int main()
{
    SIrrlichtCreationParameters params;
    params.AntiAlias = 0;
    params.Bits = 16;
    params.Fullscreen = false;
    params.WindowSize = dimension2d<u32>(640, 480);
    params.DriverType = video::EDT_OPENGL;

    IrrlichtDevice *device = createDeviceEx(params);

	if (!device)
		return 1;

    device->setWindowCaption(L"OpenGL Lines Test");

	IVideoDriver* driver = device->getVideoDriver();
	ISceneManager* smgr = device->getSceneManager();

	IAnimatedMesh* mesh = smgr->getMesh("../../media/sydney.md2");
	if (!mesh){
		device->drop();
		return 1;
	}
	IAnimatedMeshSceneNode* node = smgr->addAnimatedMeshSceneNode( mesh );


    if (node)
	{
		node->setMaterialFlag(EMF_LIGHTING, false);
		node->setMD2Animation(scene::EMAT_STAND);
		node->setMaterialTexture( 0, driver->getTexture("../../media/sydney.bmp") );
	}

	smgr->addCameraSceneNode(0, vector3df(0,30,-40), vector3df(0,5,0));

	SMaterial mat;
	mat.Thickness = 5;
    mat.AntiAliasing = 0;
    node->getMaterial(0).AntiAliasing = 0;

	while(device->run())
	{
		driver->beginScene(true, true, SColor(255,100,101,140));

		smgr->drawAll();

		driver->draw3DBox(node->getBoundingBox(), SColor(0,255,0,0));
		driver->setMaterial(mat);
		driver->draw2DLine(position2di(10,10), position2di(100,100), SColor(255,0,0,0));


		driver->endScene();
	}

	device->drop();

    return 0;
}

My application is more complex so I don't really now why and when this happens. The above code works corectly because of this lines:

Code: Select all

mat.AntiAliasing = 0;
node->getMaterial(0).AntiAliasing = 0;

the result is:


If I remove those lines or only one of them the result is:

If I remove this line:

Code: Select all

driver->draw2DLine(position2di(10,10), position2di(100,100), SColor(255,0,0,0));

then everything renders ok.

It also looks like "mat.Thickness = 5;" doesn't work. Makes no difference if it 0,1,2,3...

In my application I render to 4 different view ports and this happens only on one of them - the first one I render. It also happens when I render to only one viewport.

PS:The above results was on the computer here at work with a very old Radeon(9550) video. I tried to enable antialias to device creation and all materials. It also renders fine as it does home but the result is as if the video card desn't support antialiasing.

[bitplane]

Thanks for the test case, I've added the bug to the tracker

[hybrid]

This was already fixed for 1.7, where you can also change the 2d material and hence get properly drawn thick lines and toggle anti-aliasing.