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# Gravity Problem

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Here is the problem I have to apply gravity before I test for collision because if I don''t I get a bounce back effect but I dont want to apply gravity if I collide with an object because if I do that then my view get pulled up (I look at the sky) If you could help me that would be great, thanks. Here is the relevent code (Its from a game engine I am working on I placed the functions in the order they are clled from the object. PS CPlayer has a CCamera object contained inside it (I think this is called a container (memory lapse) void CCamera::Animate(scalar_t deltaTime) { CVector cross; CVector axis; // speed is velocity z-component float speed = velocity.z * deltaTime; gravity = -4; // strafe speed is velocity x-component float strafeSpeed = velocity.x * deltaTime; //friction if (Magnitude(velocity) > 0.0) acceleration = -velocity * 5.0f; velocity += acceleration*deltaTime; //get view view.x = lookAt.x - position.x; view.y = lookAt.y - position.y; view.z = lookAt.z - position.z; //rotate view axis = Cross(view, up); axis = Normalize(axis); RotateView(pitch, axis.x, axis.y, axis.z); RotateView(yaw, 0, 1, 0); //move camera position.x += view.x * speed; position.z += view.z * speed; position.y += gravity; lookAt.x += view.x * speed; lookAt.z += view.z * speed; //strafe cross = Cross(up, view); position.x += cross.x * strafeSpeed; position.z += cross.z * strafeSpeed; lookAt.x += cross.x * strafeSpeed; lookAt.z += cross.z * strafeSpeed; } void CPlayer::CheckCollision() { CVector offset; CVector verts[4]; verts[0].x = -100; verts[0].y = 0.0; verts[0].z = -100; verts[1].x = -100; verts[1].y = 0.0f; verts[1].z = 100; verts[2].x = 100; verts[2].y = 0; verts[2].z = 100; verts[3].x = 100; verts[3].y = 0; verts[3].z = -100; float radius = 1.0; CVector quad[4] = { verts[0], verts[1], verts[2], verts[3]}; CVector normal = Normal(quad); float distance = 0.0f; position -= CVector(0, 2, 0); int classification = ClassifySphere(position , normal, quad[0], radius, distance); if(classification == INTERSECTS) { offset = normal * distance; CVector intersection = position - offset; if(InsidePolygon(intersection, quad, 4) || EdgeSphereCollision(position, quad, 4, radius / 2)) { offset = GetCollisionOffset(normal, radius, distance); camera->position = camera->position + offset; camera->lookAt = camera->lookAt + offset; } } } void CCamera:ositionCamera() { gluLookAt(position.x, position.y, position.z, lookAt.x, lookAt.y, lookAt.z, 0.0, 1.0, 0.0); }

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quote:

position.y += gravity;

Gravity is an acceleration (force), not a velocity.

You should apply the gravity to the velocity and not the position. That should fix the problems since you only then need deal with a single velocity changing the position.

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