[eyal282]

Works, unless I look straight up, in which the grenade is fired 0.0 degrees to my right

		new Float:EyePosition[3], Float:EyeAngles[3];
	
		new grenade = CreateEntityByName("smokegrenade_projectile");
		
		GetClientEyePosition(client, EyePosition);
			
		GetClientEyeAngles(client, EyeAngles);
		
		EyeAngles[1] += 2.5;

		new Float:Velocity[3]; // Determine velocity based on given speed/angle
		GetAngleVectors(EyeAngles, Velocity, NULL_VECTOR, NULL_VECTOR);
		
		ScaleVector(Velocity, 800.0); 
		
		GetVectorAngles(Velocity, EyeAngles); // This variable won't be used again so we can steal it for this operation
		
		EyeAngles[0] += 90.0;
		
		TeleportEntity(grenade, EyePosition, EyeAngles, Velocity);
		
		//SetEntPropVector(grenade, Prop_Data, "m_angRotation", EyeAngles);
		
		DispatchSpawn(grenade);
		
		ActivateEntity(grenade);
		
		SetEntPropEnt(grenade, Prop_Send, "m_hThrower", client);

[eyal282]

I've been experimenting with right vectors and up vectors. How would I be able to merge them into a forward vector after altering one or both of them?

[mrmatthew2k]

Not exactly sure what you're describing. I also am not familiar with conventions of csgo's vectors. But keep in mind that the radius about the z axis is small when looking straight up. So it makes sense that the trajectory is the same. Also keep in mind some angle restrictions: the angle between the x-y plane and z axis only ranges from -90 to 90.

EyeAngles[0] += 90.0;

I've been experimenting with right vectors and up vectors. How would I be able to merge them into a forward vector after altering one or both of them?

Not sure what you mean by this, but you can add the vectors part by part using

void AddVectors(const float vec1[3], const float vec2[3], float result[3])