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GeoKureli

particle effects billboarding issue[C++]

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I've included pictures of whats happening as well as my "particle" image. The issue is i have a bunch a billboards showing a particle, but the alpha doesn't seem to be working in some cases, but it works in some cases. for instance if i stack the particleThis is an assignment I have for class

[source lang="cpp"]
// render the grid
d3ddev->SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
render_grid();

d3ddev->SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);

// calculate elapsed time
static DWORD starting_point = GetTickCount(), time;
time = GetTickCount() - starting_point;
starting_point = GetTickCount();

addParticles();

// prepare particle for rendering
Node<Particle> *particle = particles.first;
D3DXMATRIX patMat;
float y = 0;
while (particle != NULL){
particle->value->run_particle(time / 1000.0f);
//particle->value->position.y = y;
if(particle->value->isDead()) particle->value->reset();
patMat = particle->value->set_particle(camx, camy, camz);
d3ddev->SetTransform(D3DTS_WORLD, &patMat);

particle->value->render_particle();

// --- NEXT
particle = particle->next;
y += .05;
}
d3ddev->EndScene();
[/source]
"particles" is a linked list, addparticles adds some particles to the list until the cap is reached, and when particle die they get reset. when i draw X amount of the particles at the same position, they all draw, andit looks like a brighter version of the particle, however when i move them randomly they loook like the images below heres the particle class:
[source lang="cpp"]#include <d3dx9.h>
float random(float max, bool negative = true){ if(negative) return cos(float(rand()))*max; /*else*/ return abs(cos(float(rand())))*max;}
// the Particle class
class Particle{
protected:
D3DXVECTOR3 velocity;
D3DXVECTOR3 acceleration;
float radius;
D3DXMATRIX matRotateX;
D3DXMATRIX matRotateY;

public:
D3DXVECTOR3 position;
Particle();
void reset();
void render_particle();
D3DXMATRIX set_particle(float camx, float camy, float camz);
void run_particle(float seconds);
bool isDead();
};

Particle :: Particle(){ reset(); }
void Particle :: reset(){
position = D3DXVECTOR3(random(0.5f), 0.0, random(0.5f));
velocity = D3DXVECTOR3(random(0.5f), random(1.0f, false)+0.5f, random(0.5f));
acceleration = D3DXVECTOR3(0.0f, 0.0f, 0.0f);
radius = random(0.5f, false)+0.5f;
}

bool Particle :: isDead(){ return radius <= 0.0f; }

// this is the function that positions, rotates, scales and renders the particle
D3DXMATRIX Particle::set_particle(float camx, float camy, float camz)
{
// Before setting the world transform, do the intense mathematics!
// a. Calculate the Differences
static float difx, dify, difz;
difx = camx - position.x;
dify = camy - position.y;
difz = camz - position.z;
// ooh, intense!

// b. Calculate the Distances
static float FlatDist, TotalDist;
FlatDist = sqrt(difx * difx + difz * difz);
TotalDist = sqrt(FlatDist * FlatDist + dify * dify);

// c. Y Rotation
D3DXMatrixIdentity(&matRotateY);
matRotateY._11 = matRotateY._33 = difz / FlatDist; // cosY
matRotateY._31 = difx / FlatDist; // sinY
matRotateY._13 = -matRotateY._31; // -sinY

// d. X Rotation
D3DXMatrixIdentity(&matRotateX);
matRotateX._22 = matRotateX._33 = FlatDist / TotalDist; // cosX
matRotateX._32 = dify / TotalDist; // sinX
matRotateX._23 = -matRotateX._32; // -sinX

// e. Tranlation
static D3DXMATRIX matTranslate;
D3DXMatrixTranslation(&matTranslate, position.x, position.y, position.z);

// f. Scaling
static D3DXMATRIX matScale;
D3DXMatrixIdentity(&matScale);
matScale._11 = matScale._22 = matScale._33 = radius;

return matScale * matRotateX * matRotateY * matTranslate;
}

// this function updates the particle
void Particle::run_particle(float seconds)
{
velocity += acceleration * seconds;
position += velocity * seconds;
radius -= seconds;
return;
}[/source] Edited by GeoKureli

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i think that has to do with the zbuffer and the blending state settings.
have a look at this article for the renderstate settings he uses for particles :)

here is the 'generic' settings

lpDevice->SetRenderState(D3DRENDERSTATE_ALPHABLENDENABLE, true);
lpDevice->SetRenderState(D3DRENDERSTATE_SRCBLEND, D3DBLEND_ONE);
lpDevice->SetRenderState(D3DRENDERSTATE_DESTBLEND, D3DBLEND_ONE);
lpDevice->SetRenderState(D3DRENDERSTATE_LIGHTING, false);
lpDevice->SetRenderState(D3DRENDERSTATE_ZWRITEENABLE, false);


Hope that helps.

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You need to sort each particle Back-To-Front to have a correct render.
You don't need to do that for additive blending because each component is added to have the final color.
Use the bubble sort which is good for particle.

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If you don't want to sort your particles back-to-front, you can use alpha-testing to reduce this effect:

dev->SetRenderState(D3DRS_ALPHAREF, (DWORD)0x00000001);
dev->SetRenderState(D3DRS_ALPHATESTENABLE, TRUE);
dev->SetRenderState(D3DRS_ALPHAFUNC, D3DCMP_GREATEREQUAL);[/quote]

This will skip completely transparent pixels from being written to the z-buffer.

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Thanks guys, it works great, and your suggestions added a lot of flair to the image. the issue was with:
d3ddev->SetRenderState(D3DRS_ZWRITEENABLE, false);
and these really made it look great!
d3ddev->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_ONE);
d3ddev->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_ONE);

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